1
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Xu G, Sun L, Wang T. Demagnetizing Ferromagnetic Catalysts to the Sabatier Optimal of Haber-Bosch Process. JACS AU 2024; 4:1405-1412. [PMID: 38665674 PMCID: PMC11040701 DOI: 10.1021/jacsau.3c00785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Revised: 02/21/2024] [Accepted: 02/22/2024] [Indexed: 04/28/2024]
Abstract
Achieving the Sabatier optimal of a chemical reaction has been the central topic in heterogeneous catalysis for a century. However, this ultimate goal was greatly hindered in previous catalyst design strategies since the active sites indeed changed. Fortunately, the magneto-catalytic effect (MCE) provides a promising solution to this long-standing challenge. Recent research suggests that the performance of ferromagnetic catalysts is capable to be promoted without changing its chemical structure. Herein, we use time-dependent density functional perturbation theory (TDDFPT) calculations to elucidate that a partially demagnetized (DM) ferromagnet could be a Sabatier optimal catalyst. Using ammonia synthesis as the model reaction, we determined the activity of Cobalt at each DM state by including the magnetic thermal excitations via magnon analysis, making the 55% DM Co to the genuine Sabatier optimal. As an essential but underexcavated phenomenon in heterogeneous catalysis, the MCE will open a new avenue to design high-performance catalysts.
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Affiliation(s)
- Gaomou Xu
- Center
of Artificial Photosynthesis for Solar Fuels and Department of Chemistry,
School of Science and Research Center for Industries of the Future, Westlake University, 600 Dunyu Road, Hangzhou 310030, Zhejiang Province, China
- Institute
of Natural Sciences, Westlake Institute
for Advanced Study, 18
Shilongshan Road, Hangzhou 310024, Zhejiang Province, China
| | - Licheng Sun
- Center
of Artificial Photosynthesis for Solar Fuels and Department of Chemistry,
School of Science and Research Center for Industries of the Future, Westlake University, 600 Dunyu Road, Hangzhou 310030, Zhejiang Province, China
- Institute
of Natural Sciences, Westlake Institute
for Advanced Study, 18
Shilongshan Road, Hangzhou 310024, Zhejiang Province, China
- Division
of Solar Energy Conversion and Catalysis at Westlake University, Zhejiang Baima Lake Laboratory, Hangzhou 310000, Zhejiang Province, China
| | - Tao Wang
- Center
of Artificial Photosynthesis for Solar Fuels and Department of Chemistry,
School of Science and Research Center for Industries of the Future, Westlake University, 600 Dunyu Road, Hangzhou 310030, Zhejiang Province, China
- Institute
of Natural Sciences, Westlake Institute
for Advanced Study, 18
Shilongshan Road, Hangzhou 310024, Zhejiang Province, China
- Division
of Solar Energy Conversion and Catalysis at Westlake University, Zhejiang Baima Lake Laboratory, Hangzhou 310000, Zhejiang Province, China
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2
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Patrick CE, Huang Y, Lewis LH, Staunton JB. Theory of Defect-Induced Crystal Field Perturbations in Rare-Earth Magnets. PHYSICAL REVIEW LETTERS 2024; 132:056703. [PMID: 38364145 DOI: 10.1103/physrevlett.132.056703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 12/20/2023] [Indexed: 02/18/2024]
Abstract
We present a theory describing the single-ion anisotropy of rare-earth (RE) magnets in the presence of point defects. Taking the RE-lean 1∶12 magnet class as a prototype, we use first-principles calculations to show how the introduction of Ti substitutions into SmFe_{12} perturbs the crystal field, generating new coefficients due to the lower symmetry of the RE environment. We then demonstrate that these perturbations can be described extremely efficiently using a screened point charge model. We provide analytical expressions for the anisotropy energy that can be straightforwardly implemented in atomistic spin dynamics simulations, meaning that such simulations can be carried out for an arbitrary arrangement of point defects. The significant crystal field perturbations calculated here demonstrate that a sample that is single phase from a structural point of view can nonetheless have a dramatically varying anisotropy profile at the atomistic level if there is compositional disorder, which may influence localized magnetic objects like domain walls or skyrmions.
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Affiliation(s)
- Christopher E Patrick
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Yixuan Huang
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - Laura H Lewis
- Department of Chemical Engineering, Northeastern University, Boston, Massachusetts 02115, USA
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, Massachusetts 02115, USA
| | - Julie B Staunton
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, United Kingdom
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3
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Sun Y, Cao Y, Hu S, Avdeev M, Wang CW, Khmelevskyi S, Ren Y, Lapidus SH, Chen X, Li Q, Deng J, Miao J, Lin K, Kuang X, Xing X. Interplanar Ferromagnetism Enhanced Ultrawide Zero Thermal Expansion in Kagome Cubic Intermetallic (Zr,Nb)Fe 2. J Am Chem Soc 2023; 145:17096-17102. [PMID: 37490643 DOI: 10.1021/jacs.3c03160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
A cubic metal exhibiting zero thermal expansion (ZTE) over a wide temperature window demonstrates significant applications in a broad range of advanced technologies but is extremely rare in nature. Here, enabled by high-temperature synthesis, we realize tunable thermal expansion via magnetic doping in the class of kagome cubic (Fd-3m) intermetallic (Zr,Nb)Fe2. A remarkably isotropic ZTE is achieved with a negligible coefficient of thermal expansion (+0.47 × 10-6 K-1) from 4 to 425 K, almost wider than most ZTE in metals available. A combined in situ magnetization, neutron powder diffraction, and hyperfine Mössbauer spectrum analysis reveals that interplanar ferromagnetic ordering contributes to a large magnetic compensation for normal lattice contraction upon cooling. Trace Fe-doping introduces extra magnetic exchange interactions that distinctly enhance the ferromagnetism and magnetic ordering temperature, thus engendering such an ultrawide ZTE. This work presents a promising ZTE in kagome metallic materials.
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Affiliation(s)
- Yanming Sun
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Yili Cao
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Shixin Hu
- Institute of Applied Magnetics, Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, People's Republic of China
| | - Maxim Avdeev
- Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234, Australia
- School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Chin-Wei Wang
- Neutron Group, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Sergii Khmelevskyi
- Research Center for Computational Materials Science and Engineering, Vienna University of Technology, Karlplatz 13, A-1040 Vienna, Austria
| | - Yang Ren
- Department of Physics, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Saul H Lapidus
- X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Xin Chen
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Qiang Li
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Jinxia Deng
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Jun Miao
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Kun Lin
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Xiaojun Kuang
- College of Chemistry and Bioengineering, Guilin University of Technology, Guilin 541006, China
| | - Xianran Xing
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
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4
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Fortunato NM, Taubel A, Marmodoro A, Pfeuffer L, Ophale I, Ebert H, Gutfleisch O, Zhang H. High-Throughput Design of Magnetocaloric Materials for Energy Applications: MM´X alloys. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023:e2206772. [PMID: 37078807 DOI: 10.1002/advs.202206772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 02/26/2023] [Indexed: 05/03/2023]
Abstract
Magnetic refrigeration offers an energy efficient and environmental friendly alternative to conventional vapor-cooling. However, its adoption depends on materials with tailored magnetic and structural properties. Here a high-throughput computational workflow for the design of magnetocaloric materials is introduced. Density functional theory calculations are used to screen potential candidates in the family of MM'X (M/M' = metal, X = main group element) compounds. Out of 274 stable compositions, 46 magnetic compounds are found to stabilize in both an austenite and martensite phase. Following the concept of Curie temperature window, nine compounds are identified as potential candidates with structural transitions, by evaluating and comparing the structural phase transition and magnetic ordering temperatures. Additionally, the use of doping to tailor magnetostructural coupling for both known and newly predicted MM'X compounds is predicted and isostructural substitution as a general approach to engineer magnetocaloric materials is suggested.
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Affiliation(s)
- Nuno M Fortunato
- Institute of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, 64287, Darmstadt, Germany
| | - Andreas Taubel
- Institute of Materials Science, Functional Materials, TU Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Alberto Marmodoro
- Institute of Physics (FZU) of the Czech Academy of Sciences, Cukrovarnická 10, Praha, 16253, Czech Republic
| | - Lukas Pfeuffer
- Institute of Materials Science, Functional Materials, TU Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Ingo Ophale
- Institute of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, 64287, Darmstadt, Germany
| | - Hebert Ebert
- Department Chemie, Universität München, Butenandstr. 5-13, 81377, München, Germany
| | - Oliver Gutfleisch
- Institute of Materials Science, Functional Materials, TU Darmstadt, Alarich-Weiss-Str. 16, 64287, Darmstadt, Germany
| | - Hongbin Zhang
- Institute of Materials Science, TU Darmstadt, Otto-Berndt-Str. 3, 64287, Darmstadt, Germany
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5
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Havela L, Legut D, Kolorenč J. Hydrogen in actinides: electronic and lattice properties. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2023; 86:056501. [PMID: 36821855 DOI: 10.1088/1361-6633/acbe50] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 02/23/2023] [Indexed: 06/18/2023]
Abstract
Hydrides of actinides, their magnetic, electronic, transport, and thermodynamic properties are discussed within a general framework of H impact on bonding, characterized by volume expansion, affecting mainly the 5fstates, and a charge transfer towards H, which influences mostly the 6dand 7sstates. These general mechanisms have diverse impact on individual actinides, depending on the degree of localization of their 5fstates. Hydrogenation of uranium yields UH2and UH3, binary hydrides that are strongly magnetic due to the 5fband narrowing and reduction of the 5f-6dhybridization. Pu hydrides become magnetic as well, mainly as a result of the stabilization of the magnetic 5f5state and elimination of the admixture of the non-magnetic 5f6component.Ab-initiocomputational analyses, which for example suggest that the ferromagnetism ofβ-UH3is rather intricate involving two non-collinear sublattices, are corroborated by spectroscopic studies of sputter-deposited thin films, yielding a clean surface and offering a variability of compositions. It is found that valence-band photoelectron spectra cannot be compared directly with the 5fnground-state density of states. Being affected by electron correlations in the excited final states, they rather reflect the atomic 5fn-1multiplets. Similar tendencies can be identified also in hydrides of binary and ternary intermetallic compounds. H absorption can be used as a tool for fine tuning of electronic structure around a quantum critical point. A new direction is represented by actinide polyhydrides with a potential for high-temperature superconductivity.
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Affiliation(s)
- Ladislav Havela
- Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - Dominik Legut
- IT4Innovations, VŠB-Technical University of Ostrava, 17. listopadu 2172/15, 708 00 Ostrava, Czech Republic
| | - Jindřich Kolorenč
- Institute of Physics (FZU), Czech Academy of Sciences, Na Slovance 2,182 00 Prague, Czech Republic
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6
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Biermair F, Mendez-Martin F, Razumovskiy VI, Moitzi F, Ressel G. Microstructure-Property Correlation and Its Evolution during Aging in an Al 4.4Co 26Cr 19Fe 18Ni 27Ti 5.6 High-Entropy Alloy. MATERIALS (BASEL, SWITZERLAND) 2023; 16:2821. [PMID: 37049114 PMCID: PMC10095688 DOI: 10.3390/ma16072821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/20/2023] [Accepted: 03/30/2023] [Indexed: 06/19/2023]
Abstract
The efficient energy use in multiple sectors of modern industry is partly based on the efficient use of high-strength, high-performance alloys that retain remarkable mechanical properties at elevated and high temperatures. High-entropy alloys (HEAs) represent the most recent class of these materials with a high potential for high-temperature high-strength applications. Aside from their chemical composition and microstructure-property relationship, limited information on the effect of heat treatment as a decisive factor for alloy design is available in the literature. This work intends to contribute to this research topic by investigating the effect of heat treatment on the microstructure and mechanical performance of an Al4.4Co26Cr19Fe18Ni27Ti5.6 HEA. The solution annealed state is compared to aged states obtained at different heat treatment times at 750 °C. The temporal evolution of the matrix and the γ'-precipitates are analyzed in terms of chemical composition, crystallography, size, shape, and volume fraction by means of scanning electron microscopy, transmission electron microscopy, and atom probe tomography. The yield strength evolution and strength contributions are calculated by classical state-of-the-art models as well as by ab-initio-based calculations of the critical resolved shear stress. The findings indicate promising mechanical properties of the investigated alloy and provide insight not only into possible strengthening mechanisms but also into the evolution of main phases during the heat treatment.
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Affiliation(s)
- Florian Biermair
- Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben, Austria (G.R.)
| | - Francisca Mendez-Martin
- Department of Materials Science, Montanuniversität Leoben, Franz-Josef Straße 18, 8700 Leoben, Austria
| | | | - Franco Moitzi
- Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben, Austria (G.R.)
| | - Gerald Ressel
- Materials Center Leoben Forschung GmbH, Roseggerstraße 12, 8700 Leoben, Austria (G.R.)
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7
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Chiral Magnetic Interactions in Small Fe Clusters Triggered by Symmetry-Breaking Adatoms. Symmetry (Basel) 2023. [DOI: 10.3390/sym15020397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The chirality of the interaction between the local magnetic moments in small transition-metal alloy clusters is investigated in the framework of density-functional theory. The Dzyaloshinskii–Moriya (DM) coupling vectors Dij between the Fe atoms in Fe2X and Fe3X with X = Cu, Pd, Pt, and Ir are derived from independent ground-state energy calculations for different noncollinear orientations of the local magnetic moments. The local-environment dependence of Dij and the resulting relative stability of different chiral magnetic orders are analyzed by contrasting the results for different adatoms X and by systematically varying the distance between the adatom X and the Fe clusters. One observes that the adatoms trigger most significant DM couplings in Fe2X, often in the range of 10–30 meV. Thus, the consequences of breaking the inversion symmetry of the Fe dimer are quantified. Comparison between the symmetric and antisymmetric Fe-Fe couplings shows that the DM couplings are about two orders of magnitude weaker than the isotropic Heisenberg interactions. However, they are in general stronger than the anisotropy of the symmetric couplings. In Fe3X, alloying induces interesting changes in both the direction and strength of the DM couplings, which are the consequence of breaking the reflection symmetry of the Fe trimer and which depend significantly on the adatom-trimer distance. A local analysis of the chirality of the electronic energy shows that the DM interactions are dominated by the spin-orbit coupling at the adatoms and that the contribution of the Fe atoms is small but not negligible.
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8
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Lu S, Sun X, Tian Y, An X, Li W, Chen Y, Zhang H, Vitos L. Theory of transformation-mediated twinning. PNAS NEXUS 2022; 2:pgac282. [PMID: 36712941 PMCID: PMC9830949 DOI: 10.1093/pnasnexus/pgac282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 12/03/2022] [Indexed: 12/12/2022]
Abstract
High-density and nanosized deformation twins in face-centered cubic (fcc) materials can effectively improve the combination of strength and ductility. However, the microscopic dislocation mechanisms enabling a high twinnability remain elusive. Twinning usually occurs via continuous nucleation and gliding of twinning partial dislocations on consecutive close-packed atomic planes. Here we unveil a completely different twinning mechanism being active in metastable fcc materials. The transformation-mediated twinning (TMT) is featured by a preceding displacive transformation from the fcc phase to the hexagonal close-packed (hcp) one, followed by a second-step transformation from the hcp phase to the fcc twin. The nucleation of the intermediate hcp phase is driven by the thermodynamic instability and the negative stacking fault energy of the metastable fcc phase. The intermediate hcp structure is characterized by the easy slips of Shockley partial dislocations on the basal planes, which leads to both fcc and fcc twin platelets during deformation, creating more twin boundaries and further enhancing the prosperity of twins. The disclosed fundamental understanding of the complex dislocation mechanism of deformation twinning in metastable alloys paves the road to design novel materials with outstanding mechanical properties.
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Affiliation(s)
- Song Lu
- To whom correspondence should be addressed:
| | - Xun Sun
- To whom correspondence should be addressed:
| | - Yanzhong Tian
- Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials Science and Engineering, Northeastern University, Shenyang 10819, China
| | - Xianghai An
- School of Aerospace, Mechanical & Mechatronic Engineering, The University of Sydney, Camperdown Sydney, NSW 2006, Australia
| | - Wei Li
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Brinellvägen 23, Stockholm, SE-10044, Sweden
| | - Yujie Chen
- School of Aerospace, Mechanical & Mechatronic Engineering, The University of Sydney, Camperdown Sydney, NSW 2006, Australia,School of Mechanical Engineering, University of Adelaide, Adelaide, SA 5005, Australia
| | | | - Levente Vitos
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Brinellvägen 23, Stockholm, SE-10044, Sweden,Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Uppsala, Box 516, SE-75121, Sweden,Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, Budapest H-1525, Hungary
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9
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Jacobsson A, Johansson G, Gorbatov OI, Ležaić M, Sanyal B, Blügel S, Etz C. Efficient parameterisation of non-collinear energy landscapes in itinerant magnets. Sci Rep 2022; 12:18987. [PMID: 36347896 PMCID: PMC9643378 DOI: 10.1038/s41598-022-20311-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 09/01/2022] [Indexed: 11/09/2022] Open
Abstract
Magnetic exchange interactions determine the magnetic groundstate, as well as magnetic excitations of materials and are thus essential to the emerging and fast evolving fields of spintronics and magnonics. The magnetic force theorem has been used extensively for studying magnetic exchange interactions. However, short-ranged interactions in itinerant magnetic systems are poorly described by this method and numerous strategies have been developed over the years to overcome this deficiency. The present study supplies a fully self-consistent method for systematic investigations of exchange interactions beyond the standard Heisenberg model. In order to better describe finite deviations from the magnetic ground state, an extended Heisenberg model, including multi-spin interactions, is suggested. Using cross-validation analysis, we show that this extended Heisenberg model gives a superior description for non-collinear magnetic configurations. This parameterisation method allows us to describe many different itinerant magnetic systems and can be useful for high-throughput calculations.
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10
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Larsen SR, Shtender V, Hedlund D, Delczeg-Czirjak EK, Beran P, Cedervall J, Vishina A, Hansen TC, Herper HC, Svedlindh P, Eriksson O, Sahlberg M. Revealing the Magnetic Structure and Properties of Mn(Co,Ge) 2. Inorg Chem 2022; 61:17673-17681. [PMID: 36270053 PMCID: PMC9644371 DOI: 10.1021/acs.inorgchem.2c02758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The atomic and magnetic structures of Mn(Co,Ge)2 are
reported herein. The system crystallizes in the space group P63/mmc as a superstructure
of the MgZn2-type structure. The system exhibits two magnetic
transitions with associated magnetic structures, a ferromagnetic (FM)
structure around room temperature, and an incommensurate structure
at lower temperatures. The FM structure, occurring between 193 and
329 K, is found to be a member of the magnetic space group P63/mm′c′. The incommensurate structure found below 193 K is helical
with propagation vector k = (0 0 0.0483). Crystallographic
results are corroborated by magnetic measurements and ab initio calculations. The new candidate material for rare-earth-free
permanent
magnets, Mn(Co,Ge)2, was investigated with neutron diffraction,
and its crystalline and magnetic structure was determined. The material
exhibits a simple ferromagnetic magnetic structure between 193 and
329 K with individual moments parallel to the c-axis.
Below 168 K, the moments arrange as a helical structure with magnetic
moments revolving around the c-axis. Theoretically
calculated values agreed well with the model and corroborated the
results.
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Affiliation(s)
- Simon R Larsen
- Department of Chemistry─Ångström, Uppsala University, Box 538, 751 21Uppsala, Sweden
| | - Vitalii Shtender
- Department of Chemistry─Ångström, Uppsala University, Box 538, 751 21Uppsala, Sweden
| | - Daniel Hedlund
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03Uppsala, Sweden
| | - Erna K Delczeg-Czirjak
- Department of Physics and Astronomy, Uppsala University, Box 516, SE75120Uppsala, Sweden
| | - Premysl Beran
- European Spallation Source ESS ERIC, Box 176, 221 00Lund, Sweden.,Nuclear Physics Institute, ASCR, Hlavni 130, 25068Rez, Czech Republic
| | - Johan Cedervall
- Department of Materials and Environmental Chemistry, Stockholm University, 10691Stockholm, Sweden
| | - Alena Vishina
- Department of Physics and Astronomy, Uppsala University, Box 516, SE75120Uppsala, Sweden
| | - Thomas C Hansen
- Institut Laue-Langevin, 71 Avenue des Martyrs, 38000Grenoble, France
| | - Heike C Herper
- Department of Physics and Astronomy, Uppsala University, Box 516, SE75120Uppsala, Sweden
| | - Peter Svedlindh
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03Uppsala, Sweden
| | - Olle Eriksson
- Department of Physics and Astronomy, Uppsala University, Box 516, SE75120Uppsala, Sweden.,School of Science and Technology, Örebro University, SE-701 82Örebro, Sweden
| | - Martin Sahlberg
- Department of Chemistry─Ångström, Uppsala University, Box 538, 751 21Uppsala, Sweden
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11
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Deák A, Jackson J, Nyári B, Szunyogh L. Incommensurate magnetic ordering in CrB 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:475801. [PMID: 36150375 DOI: 10.1088/1361-648x/ac94b0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Incommensurate magnetism in CrB2is studied in terms of a spin model based on density functional theory calculations. Heisenberg exchange interactions derived from the paramagnetic phase using the disordered local moment (DLM) theory show significant differences compared with those resulting from the treatment of the material as a ferromagnet; of these two methods, the DLM theory is found to give a significantly more realistic description. We calculate strongly ferromagnetic interactions between Cr planes but largely frustrated interactions within Cr planes. Although we find that the ground state ordering vector is sensitive to exchange interactions over a large number of neighbour shells, theq-vector of the incommensurate spin spiral state is satisfactorily reproduced by the theory (0.213 compared with the known ordering vector0.285×(2π)/(a/2)along Γ-K). The strong geometric frustration of the exchange interactions causes a rather low Néel temperature (about 97 K), also in good agreement with experiment.
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Affiliation(s)
- A Deák
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
| | - J Jackson
- STFC Scientific Computing Department, Daresbury Laboratory, WA4 4AD Warrington, United Kingdom
| | - B Nyári
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
- ELKH-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
| | - L Szunyogh
- Department of Theoretical Physics, Institute of Physics, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
- ELKH-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Műegyetem rkp. 3, H-1111 Budapest, Hungary
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12
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Gendron F, Cliche N, Amadon B. Role of pressure on electronic, magnetic and structural properties at iron's Curie temperature: a DFT + DMFT study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:464003. [PMID: 36067782 DOI: 10.1088/1361-648x/ac8fd0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 09/06/2022] [Indexed: 06/15/2023]
Abstract
We use the combination of density functional theory and dynamical mean-field theory to compute the Curie temperature of the iron body-centered cubicαphase and probe its pressure dependence. Our calculations reveal thatTCshows a decrease which is very weak over a domain of pressures that is much larger than the stability domain of theαphase. This is consistent with the experimental results. We highlight the importance of the Hund's couplingJnot only on the electronic and magnetic properties but also on the structural properties. Lastly, we analyze the electronic and magnetic properties under pressure and discuss the evolution of magnetic moments in both phases in relation to the change of Curie temperature.
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Affiliation(s)
- F Gendron
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoire Matière en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
| | - N Cliche
- CEA, DAM, DIF, F-91297 Arpajon, France
| | - B Amadon
- CEA, DAM, DIF, F-91297 Arpajon, France
- Université Paris-Saclay, CEA, Laboratoire Matière en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
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13
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Thermodynamics and Magnetism of SmFe12 Compound Doped with Co and Ni: An Ab Initio Study. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12104860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ni-doped Sm(Fe1−xCox)12 alloys are investigated for their magnetic properties. The Sm(Fe,Co)11M1 compound (M acts as a stabilizer) with the smallest (7.7 at.%) rare-earth-metal content has been recognized as a possible contender for highly efficient permanent magnets thanks to its significant anisotropy field and Curie temperature. The early transition metals (Ti-Mn) as well as Al, Si, and Ga stabilize the SmFe12 compound but significantly decrease its saturation magnetization. To keep the saturation magnetization in the range of 1.4–1.6 T, we suggest replacing a certain amount of Fe and Co in the Sm(Fe1−xCox)12 alloys with Ni. Ni plays the role of a thermodynamic stabilizer, and contrary to the above-listed elements, has the spin moment aligned parallel to the spin moment of the SmFe12 compound, thereby boosting its saturation magnetization without affecting the anisotropy field or Curie temperature.
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14
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Bouaziz J, Mendive-Tapia E, Blügel S, Staunton JB. Fermi-Surface Origin of Skyrmion Lattices in Centrosymmetric Rare-Earth Intermetallics. PHYSICAL REVIEW LETTERS 2022; 128:157206. [PMID: 35499873 DOI: 10.1103/physrevlett.128.157206] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 03/11/2022] [Indexed: 06/14/2023]
Abstract
We show from first principles that barrel-shaped structures within the Fermi surface of the centrosymmetric intermetallic compounds GdRu_{2}Si_{2} and Gd_{2}PdSi_{3} give rise to Fermi surface nesting, which determines the strength and sign of quasi-two-dimensional Ruderman-Kittel-Kasuya-Yosida pairwise exchange interactions between the Gd moments. This is the principal mechanism leading to their helical single-q spin-spiral ground states, providing transition temperatures and magnetic periods in good agreement with experiment. Using atomistic spin-dynamic simulations, we draw a direct line between the subtleties of the three-dimensional Fermi surface topology and the stabilization of a square skyrmion lattice in GdRu_{2}Si_{2} at applied magnetic fields as observed in experiment.
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Affiliation(s)
- Juba Bouaziz
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Eduardo Mendive-Tapia
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
- Department of Computational Materials Design, Max-Planck-Institut für Eisenforschung, 40237 Düsseldorf, Germany
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - Julie B Staunton
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
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15
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Ye X, Fortunato N, Sarkar A, Geßwein H, Wang D, Chen X, Eggert B, Wende H, Brand RA, Zhang H, Hahn H, Kruk R. Creating a Ferromagnetic Ground State with T c Above Room Temperature in a Paramagnetic Alloy through Non-Equilibrium Nanostructuring. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108793. [PMID: 34856022 DOI: 10.1002/adma.202108793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/24/2021] [Indexed: 06/13/2023]
Abstract
Materials with strong magnetostructural coupling have complex energy landscapes featuring multiple local ground states, thus making it possible to switch among distinct magnetic-electronic properties. However, these energy minima are rarely accessible by a mere application of an external stimuli to the system in equilibrium state. A ferromagnetic ground state, with Tc above room temperature, can be created in an initially paramagnetic alloy by nonequilibrium nanostructuring. By a dealloying process, bulk chemically disordered FeRh alloys are transformed into a nanoporous structure with the topology of a few nanometer-sized ligaments and nodes. Magnetometry and Mössbauer spectroscopy reveal the coexistence of two magnetic ground states, a conventional low-temperature spin-glass and a hitherto-unknown robust ferromagnetic phase. The emergence of the ferromagnetic phase is validated by density functional theory calculations showing that local tetragonal distortion induced by surface stress favors ferromagnetic ordering. The study provides a means for reaching conventionally inaccessible magnetic states, resulting in a complete on/off ferromagnetic-paramagnetic switching over a broad temperature range.
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Affiliation(s)
- Xinglong Ye
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - Nuno Fortunato
- Institute of Materials Science, Technische Universität Darmstadt, 64287, Darmstadt, Germany
| | - Abhishek Sarkar
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
- Institute of Materials Science, Technische Universität Darmstadt, 64287, Darmstadt, Germany
| | - Holger Geßwein
- Institute for Applied Materials, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - Di Wang
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
- Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany
| | - Xiang Chen
- Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Benedikt Eggert
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Heiko Wende
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Richard A Brand
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, 47057, Duisburg, Germany
| | - Hongbin Zhang
- Institute of Materials Science, Technische Universität Darmstadt, 64287, Darmstadt, Germany
| | - Horst Hahn
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
| | - Robert Kruk
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344, Eggenstein-Leopoldshafen, Germany
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16
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Gebresenbut GH, Eriksson L, Häussermann U, Rydh A, Mathieu R, Vekilova OY, Shiino T. Superconducting YAu 3Si and Antiferromagnetic GdAu 3Si with an Interpenetrating Framework Structure Built from 16-Atom Polyhedra. Inorg Chem 2022; 61:4322-4334. [PMID: 35225597 PMCID: PMC8924926 DOI: 10.1021/acs.inorgchem.1c03456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Investigations of
reaction mixtures REx(Au0.79Si0.21)100–x (RE =
Y and Gd) yielded the compounds REAu3Si which
adopt a new structure type, referred to as GdAu3Si structure
(tP80, P42/mnm, Z = 16, a = 12.8244(6)/12.7702(2)
Å, and c = 9.0883(8)/9.0456(2) Å for GdAu3Si/YAu3Si, respectively). REAu3Si was
afforded as millimeter-sized faceted crystal specimens from solution
growth employing melts with composition RE18(Au0.79Si0.21)82. In the GdAu3Si structure,
the Au and Si atoms are strictly ordered and form a framework built
of corner-connected, Si-centered, trigonal prismatic units SiAu6. RE atoms distribute on 3 crystallographically different
sites and each attain a 16-atom coordination by 12 Au and 4 Si atoms.
These 16-atom polyhedra commonly fill the space of the unit cell.
The physical properties of REAu3Si were investigated by
heat capacity, electrical resistivity, and magnetometry techniques
and are discussed in the light of theoretical predictions. YAu3Si exhibits superconductivity around 1 K, whereas GdAu3Si shows a complex magnetic ordering, likely related to frustrated
antiferromagnets exhibiting chiral spin textures. GdAu3Si-type phases with interesting magnetic and transport properties
may exist in an extended range of ternary RE–Au–Si systems,
similar to the compositionally adjacent cubic 1/1 approximants RE(Au,Si)∼6. A novel structure
type, tP80 and P42/mnm, is discovered in two
compounds: GdAu3Si and YAu3Si. The crystal structure
was determined using SCXRD technique. Physical properties of both
compounds were investigated experimentally by heat capacity, electrical
resistivity, and magnetometry techniques and theoretically using the
DFT method. While the GdAu3Si prevail complex magnetic
ordering at the temperature around 10 K, YAu3Si becomes
superconducting close to 1 K.
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Affiliation(s)
| | - Lars Eriksson
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Ulrich Häussermann
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Andreas Rydh
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Roland Mathieu
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03 Uppsala, Sweden
| | - Olga Yu Vekilova
- Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm, Sweden
| | - Takayuki Shiino
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03 Uppsala, Sweden
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17
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Critical dynamics and phase transition of a strongly interacting warm spin gas. Proc Natl Acad Sci U S A 2021; 118:2106400118. [PMID: 34686598 DOI: 10.1073/pnas.2106400118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2021] [Indexed: 11/18/2022] Open
Abstract
Phase transitions are emergent phenomena where microscopic interactions drive a disordered system into a collectively ordered phase. Near the boundary between two phases, the system can exhibit critical, scale-invariant behavior. Here, we report on a second-order phase transition accompanied by critical behavior in a system of warm cesium spins driven by linearly polarized light. The ordered phase exhibits macroscopic magnetization when the interactions between the spins become dominant. We measure the phase diagram of the system and observe the collective behavior near the phase boundaries, including power-law dependence of the magnetization and divergence of the susceptibility. Out of equilibrium, we observe a critical slowdown of the spin response time by two orders of magnitude, exceeding 5 s near the phase boundary. This work establishes a controlled platform for investigating equilibrium and nonequilibrium properties of magnetic phases.
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18
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Miyake T, Harashima Y, Fukazawa T, Akai H. Understanding and optimization of hard magnetic compounds from first principles. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2021; 22:543-556. [PMID: 34552388 PMCID: PMC8451637 DOI: 10.1080/14686996.2021.1935314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 05/11/2021] [Accepted: 05/24/2021] [Indexed: 06/13/2023]
Abstract
First-principles calculation based on density functional theory is a powerful tool for understanding and designing magnetic materials. It enables us to quantitatively describe magnetic properties and structural stability, although further methodological developments for the treatment of strongly correlated 4f electrons and finite-temperature magnetism are needed. Here, we review recent developments of computational schemes for rare-earth magnet compounds, and summarize our theoretical studies on Nd2Fe14B and RFe12-type compounds. Effects of chemical substitution and interstitial dopants are clarified. We also discuss how data-driven approaches are used for studying multinary systems. Chemical composition can be optimized with fewer trials by the Bayesian optimization. We also present a data-assimilation method for predicting finite-temperature magnetization in wide composition space by integrating computational and experimental data.
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Affiliation(s)
- Takashi Miyake
- Research Center for Computational Design of Advanced Functional Materials, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
- Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Yosuke Harashima
- Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan
- Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Japan
| | - Taro Fukazawa
- Research Center for Computational Design of Advanced Functional Materials, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
- Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Hisazumi Akai
- Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba, Japan
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan
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19
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Fedorov AV, Poelchen G, Eremeev SV, Schulz S, Generalov A, Polley C, Laubschat C, Kliemt K, Kaya N, Krellner C, Chulkov EV, Kummer K, Usachov DY, Ernst A, Vyalikh DV. Insight into the Temperature Evolution of Electronic Structure and Mechanism of Exchange Interaction in EuS. J Phys Chem Lett 2021; 12:8328-8334. [PMID: 34428055 DOI: 10.1021/acs.jpclett.1c02274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Discovered in 1962, the divalent ferromagnetic semiconductor EuS (TC = 16.5 K, Eg = 1.65 eV) has remained constantly relevant to the engineering of novel magnetically active interfaces, heterostructures, and multilayer sequences and to combination with topological materials. Because detailed information on the electronic structure of EuS and, in particular, its evolution across TC is not well-represented in the literature but is essential for the development of new functional systems, the present work aims at filling this gap. Our angle-resolved photoemission measurements complemented with first-principles calculations demonstrate how the electronic structure of EuS evolves across a paramagnetic-ferromagnetic transition. Our results emphasize the importance of the strong Eu 4f-S 3p mixing for exchange-magnetic splittings of the sulfur-derived bands as well as coupling between f and d orbitals of neighboring Eu atoms to derive the value of TC accurately. The 4f-3p mixing facilitates the coupling between 4f and 5d orbitals of neighboring Eu atoms, which mainly governs the exchange interaction in EuS.
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Affiliation(s)
- A V Fedorov
- Leibniz Institute for Solid State and Materials Research, 01069 Dresden, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - G Poelchen
- Institut für Festkörper- und Materialphysik, TU Dresden, 01069 Dresden, Germany
- European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - S V Eremeev
- Institute of Strength Physics and Materials Science, 634055 Tomsk, Russia
| | - S Schulz
- Institut für Festkörper- und Materialphysik, TU Dresden, 01069 Dresden, Germany
| | - A Generalov
- Max IV Laboratory, Lund University, Box 118, 22100 Lund, Sweden
| | - C Polley
- Max IV Laboratory, Lund University, Box 118, 22100 Lund, Sweden
| | - C Laubschat
- Institut für Festkörper- und Materialphysik, TU Dresden, 01069 Dresden, Germany
| | - K Kliemt
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - N Kaya
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - C Krellner
- Kristall- und Materiallabor, Physikalisches Institut, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - E V Chulkov
- Tomsk State University, 634050 Tomsk, Russia
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Facultad de Ciencias Químicas, Universidad del País Vasco UPV/EHU, 20080 San Sebastián/Donostia, Spain
- Centro de Física de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, 20018 San Sebastián/Donostia, Spain
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - K Kummer
- European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - D Yu Usachov
- St. Petersburg State University, St. Petersburg, 199034, Russia
| | - A Ernst
- Institut für Theoretische Physik, Johannes Kepler Universität, A 4040 Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, D-06120 Halle, Germany
| | - D V Vyalikh
- Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
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20
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Jang TJ, Choi WS, Kim DW, Choi G, Jun H, Ferrari A, Körmann F, Choi PP, Sohn SS. Shear band-driven precipitate dispersion for ultrastrong ductile medium-entropy alloys. Nat Commun 2021; 12:4703. [PMID: 34349105 PMCID: PMC8338972 DOI: 10.1038/s41467-021-25031-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 07/13/2021] [Indexed: 11/02/2022] Open
Abstract
Precipitation strengthening has been the basis of physical metallurgy since more than 100 years owing to its excellent strengthening effects. This approach generally employs coherent and nano-sized precipitates, as incoherent precipitates energetically become coarse due to their incompatibility with matrix and provide a negligible strengthening effect or even cause brittleness. Here we propose a shear band-driven dispersion of nano-sized and semicoherent precipitates, which show significant strengthening effects. We add aluminum to a model CoNiV medium-entropy alloy with a face-centered cubic structure to form the L21 Heusler phase with an ordered body-centered cubic structure, as predicted by ab initio calculations. Micro-shear bands act as heterogeneous nucleation sites and generate finely dispersed intragranular precipitates with a semicoherent interface, which leads to a remarkable strength-ductility balance. This work suggests that the structurally dissimilar precipitates, which are generally avoided in conventional alloys, can be a useful design concept in developing high-strength ductile structural materials.
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Affiliation(s)
- Tae Jin Jang
- Department of Materials Science and Engineering Korea University, Seoul, South Korea
| | - Won Seok Choi
- Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Dae Woong Kim
- Center for High Entropy Alloys Pohang University of Science and Technology, Pohang, South Korea
| | - Gwanghyo Choi
- Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Hosun Jun
- Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology, Daejeon, South Korea
| | - Alberto Ferrari
- Department of Materials Science and Engineering Delft University of Technology, Mekelweg 2, Delft, The Netherlands
| | - Fritz Körmann
- Department of Materials Science and Engineering Delft University of Technology, Mekelweg 2, Delft, The Netherlands.,Max-Planck-Institut für Eisenforschung Max-Planck-Straße 1, Düsseldorf, Germany
| | - Pyuck-Pa Choi
- Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology, Daejeon, South Korea.
| | - Seok Su Sohn
- Department of Materials Science and Engineering Korea University, Seoul, South Korea.
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21
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Cao Y, Lin K, Khmelevskyi S, Avdeev M, Taddei KM, Zhang Q, Huang Q, Li Q, Kato K, Tang CC, Gibbs A, Wang CW, Deng J, Chen J, Zhang H, Xing X. Ultrawide Temperature Range Super-Invar Behavior of R_{2}(Fe,Co)_{17} Materials (R = Rare Earth). PHYSICAL REVIEW LETTERS 2021; 127:055501. [PMID: 34397222 DOI: 10.1103/physrevlett.127.055501] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 06/23/2021] [Indexed: 06/13/2023]
Abstract
Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R_{2}(Fe,Co)_{17} materials (R=rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3-461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve "ultrawide" SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials.
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Affiliation(s)
- Yili Cao
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Kun Lin
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Sergii Khmelevskyi
- Research Center for Computational Materials Science and Engineering, Vienna University of Technology, Karlplatz 13, A-1040 Vienna, Austria
| | - Maxim Avdeev
- Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | - Keith M Taddei
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Qiang Zhang
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Qingzhen Huang
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA
| | - Qiang Li
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | | | | | - Alexandra Gibbs
- ISIS Neutron and Muon Source, Science and Technology Facilities Council, Didcot OX11 0QX, United Kingdom
| | - Chin-Wei Wang
- Neutron Group, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Jinxia Deng
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Jun Chen
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Hongjie Zhang
- State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
| | - Xianran Xing
- Beijing Advanced Innovation Center for Materials Genome Engineering, Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
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22
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Pei Z, Dutta B, Körmann F, Chen M. Hidden Effects of Negative Stacking Fault Energies in Complex Concentrated Alloys. PHYSICAL REVIEW LETTERS 2021; 126:255502. [PMID: 34241525 DOI: 10.1103/physrevlett.126.255502] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 05/20/2021] [Indexed: 06/13/2023]
Abstract
Negative stacking fault energies (SFEs) are found in face-centered cubic high-entropy alloys with excellent mechanical properties, especially at low temperatures. Their roles remain elusive due to the lack of in situ observation of nanoscale deformation. Here, the polymorphism of Shockley partials is fully explored, assisted by a new method. We show negative SFEs result in novel partial pairs as if they were in hexagonal close-packed alloys. The associated yield stresses are much higher than those for other mechanisms at low temperatures. This generalizes the physical picture for all negative-SFE alloys.
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Affiliation(s)
- Zongrui Pei
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Biswanath Dutta
- Department of Materials Science and Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Fritz Körmann
- Department of Materials Science and Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands and Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany
| | - Mingwei Chen
- Department of Materials Science and Engineering and Hopkins Extreme Materials Institute, Johns Hopkins University, Baltimore, Maryland 21218, USA
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23
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Invariant plastic deformation mechanism in paramagnetic nickel-iron alloys. Proc Natl Acad Sci U S A 2021; 118:2023181118. [PMID: 33782128 DOI: 10.1073/pnas.2023181118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Invar anomaly is one of the most fascinating phenomena observed in magnetically ordered materials. Invariant thermal expansion and elastic properties have attracted substantial scientific attention and led to important technological solutions. By studying planar faults in the high-temperature magnetically disordered state of [Formula: see text], here we disclose a completely different anomaly. An invariant plastic deformation mechanism is characterized by an unchanged stacking fault energy with temperature within wide concentration and temperature ranges. This anomaly emerges from the competing stability between the face-centered cubic and hexagonal close-packed structures and occurs in other paramagnetic or nonmagnetic systems whenever the structural balance exists. The present findings create a platform for tailoring high-temperature properties of technologically relevant materials toward plastic stability at elevated temperatures.
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24
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Gerasimov A, Nordström L, Khmelevskyi S, Mazurenko VV, Kvashnin YO. Nature of the magnetic moment of cobalt in ordered FeCo alloy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:165801. [PMID: 33724237 DOI: 10.1088/1361-648x/abdfff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
The magnets are typically classified into Stoner and Heisenberg type, depending on the itinerant or localized nature of the constituent magnetic moments. In this work, we investigate theoretically the behaviour of the magnetic moments of iron and cobalt in their B2-ordered alloy. The results based on local spin density approximation for the density functional theory (DFT) suggest that the Co magnetic moment strongly depends on the directions of the surrounding magnetic moments, which usually indicates the Stoner-type mechanism of magnetism. This is consistent with the disordered local moment picture of the paramagnetic state, where the magnetic moment of cobalt gets substantially suppressed. We argue that this is due to the lack of strong on-site electron correlations, which we take into account by employing a combination of DFT and dynamical mean-field theory (DMFT). Within LDA + DMFT, we find a substantial quasiparticle mass renormalization and a non Fermi-liquid behaviour of Fe-3dorbitals. The resulting spectral functions are in very good agreement with measured spin-resolved photoemission spectra. Our results suggest that local correlations play an essential role in stabilizing a robust local moment on Co in the absence of magnetic order at high temperatures.
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Affiliation(s)
- Arsenii Gerasimov
- Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia
| | - Lars Nordström
- Uppsala University, Department of Physics and Astronomy, Division of Materials Theory, Box 516, SE-751 20 Uppsala, Sweden
| | - Sergii Khmelevskyi
- Center for Computational Materials Science, Institute for Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8, A-1040, Vienna, Austria
| | - Vladimir V Mazurenko
- Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia
| | - Yaroslav O Kvashnin
- Uppsala University, Department of Physics and Astronomy, Division of Materials Theory, Box 516, SE-751 20 Uppsala, Sweden
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25
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Zhang Z, Yang Z, Lu S, Harte A, Morana R, Preuss M. Strain localisation and failure at twin-boundary complexions in nickel-based superalloys. Nat Commun 2020; 11:4890. [PMID: 32994396 PMCID: PMC7524752 DOI: 10.1038/s41467-020-18641-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 08/21/2020] [Indexed: 11/18/2022] Open
Abstract
Twin boundaries (TBs) in Ni-based superalloys are vulnerable sites for failure in demanding environments, and a current lack of mechanistic understanding hampers the reliable lifetime prediction and performance optimisation of these alloys. Here we report the discovery of an unexpected γ″ precipitation mechanism at TBs that takes the responsibility for alloy failure in demanding environments. Using multiscale microstructural and mechanical characterisations (from millimetre down to atomic level) and DFT calculations, we demonstrate that abnormal γ″ precipitation along TBs accounts for the premature dislocation activities and pronounced strain localisation associated with TBs during mechanical loading, which serves as a precursor for crack initiation. We clarify the physical origin of the TBs-related cracking at the atomic level of γ″-strengthened Ni-based superalloys in a hydrogen containing environment, and provide practical methods to mitigate the adverse effect of TBs on the performance of these alloys. Coherent twin boundaries in nickel-based superalloys are vulnerable sites for alloy failure in demanding environments. Here, the authors show that the abnormal γ″ precipitation mechanism at twin boundaries is responsible for pronounced strain localisation and subsequent failure.
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Affiliation(s)
- Zhenbo Zhang
- School of Materials, University of Manchester, M13 9PL, Manchester, UK. .,Center for Adaptative System Engineering, School of Creativity and Arts, ShanghaiTech University, Shanghai, 201210, China.
| | - Zhibiao Yang
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, SE, 100 44, Sweden.,Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China
| | - Song Lu
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm, SE, 100 44, Sweden
| | - Allan Harte
- School of Materials, University of Manchester, M13 9PL, Manchester, UK
| | - Roberto Morana
- BP Exploration Operating Company Limited, Chertsey Road, Sunbury-on-Thames, TW16 7LN, Sunbury, UK
| | - Michael Preuss
- School of Materials, University of Manchester, M13 9PL, Manchester, UK.
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26
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Thermodynamics and Magnetism of YCo5 Compound Doped with Fe and Ni: An Ab Initio Study. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10176037] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
YCo5 permanent magnet exhibits high uniaxial magnetocrystalline anisotropy energy and has a high Curie temperature. These are good properties for a permanent magnet, but YCo5 has a low energy product, which is notably insufficient for a permanent magnet. In order to improve the energy product in YCo5, we suggest replacing cobalt with iron, which has a much bigger magnetic moment. With a combination of density-functional-theory calculations and thermodynamic CALculation of PHAse Diagrams (CALPHAD) modeling, we show that a new magnet, YFe3(Ni1-xCox)2, is thermodynamically stable and exhibits an improved energy product without significant detrimental effects on the magnetocrystalline anisotropy energy or the Curie temperature.
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27
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Tian F, Yang Z, Lin DY, Zhao YF. Lattice distortion inducing local antiferromagnetic behaviors in FeAl alloys. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:465805. [PMID: 32841211 DOI: 10.1088/1361-648x/abae1b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 08/11/2020] [Indexed: 06/11/2023]
Abstract
In this work, we study the local magnetic moment as a function of order degree in solid-solution FeAl alloys. Using the combination ofab initiomethod and similar atomic environment model, we find that the decrease of magnetic moment, even antiferromagnetic behavior, of the Fe atoms derives from the distorted local atomic clusters centered at Fe atoms on the Fe-atom sublattice sites in B2 FeAl alloys. While the local magnetic moment of Fe atoms is up to 2.2μBon the Al and Fe solid-solution sublattice sites. The ordering results in the decrease of Curie temperature and magnetic moment of solid-solution FeAl alloys.
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Affiliation(s)
- Fuyang Tian
- Institute for Applied Physics, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, University of Science and Technology Beijing, 100083, Beijing
| | - Zhen Yang
- Institute for Applied Physics, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, University of Science and Technology Beijing, 100083, Beijing
| | - De-Ye Lin
- Software Center for High Performance Numerical Simulation, Beijing 100088, People's Republic of China
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China
| | - Ya-Fan Zhao
- Software Center for High Performance Numerical Simulation, Beijing 100088, People's Republic of China
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China
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28
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Tian F, Lin DY, Gao X, Zhao YF, Song HF. A structural modeling approach to solid solutions based on the similar atomic environment. J Chem Phys 2020; 153:034101. [PMID: 32716184 DOI: 10.1063/5.0014094] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A solid solution is one of the important ways to enhance the structural and functional performance of materials. In this work, we develop a structural modeling approach to solid solutions based on the similar atomic environment (SAE). We propose a similarity function associated with any type of atom cluster to describe quantitatively the configurational deviation from the desired solid-solution structure that is fully disordered or contains short-range order (SRO). In this manner, the structural modeling for solid solutions is transferred to a minimization problem in the configuration space. Moreover, we strive to enhance the practicality of this approach. The approach and implementation are demonstrated by cross validations with the special quasi-random structure method. We apply the SAE method to the typical quinary CoCrFeMnNi high-entropy alloy, continuous binary Ta-W alloy, and ternary CoCrNi medium-entropy alloy with SRO as prototypes. In combination with ab initio calculations, we investigate the structural properties and compare the calculation results with experiments.
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Affiliation(s)
- Fuyang Tian
- Institute for Applied Physics, Beijing Key Laboratory for Magneto-Photoelectrical Composite and Interface Science, University of Science and Technology Beijing, Beijing 100083, China
| | - De-Ye Lin
- CAEP Software Center for High Performance Numerical Simulation, Beijing 100088, China
| | - Xingyu Gao
- Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
| | - Ya-Fan Zhao
- CAEP Software Center for High Performance Numerical Simulation, Beijing 100088, China
| | - Hai-Feng Song
- CAEP Software Center for High Performance Numerical Simulation, Beijing 100088, China
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29
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Dahlqvist M, Rosen J. Impact of strain, pressure, and electron correlation on magnetism and crystal structure of Mn 2GaC from first-principles. Sci Rep 2020; 10:11384. [PMID: 32647126 PMCID: PMC7347948 DOI: 10.1038/s41598-020-68377-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 06/10/2020] [Indexed: 11/20/2022] Open
Abstract
The atomically laminated Mn2GaC has previously been synthesized as a heteroepitaxial thin film and found to be magnetic with structural changes linked to the magnetic anisotropy. Related theoretical studies only considered bulk conditions and thus neglected the influence from possible strain linked to the choice of substrate. Here we employ first principles calculations considering different exchange-correlation functionals (PBE, PW91, PBEsol, AM05, LDA) and effect from use of + U methods (or not) combined with a magnetic ground-state search using Heisenberg Monte Carlo simulations, to study influence from biaxial in-plane strain and external pressure on the magnetic and crystal structure of Mn2GaC. We find that PBE and PBE + U, with Ueff ≤ 0.25 eV, gives both structural and magnetic properties in quantitative agreement with available experimental data. Our results also indicate that strain related to choice of substrate or applied pressure is a route for accessing different spin configurations, including a ferromagnetic state. Moreover, the easy axis is parallel to the atomic planes and the magnetocrystalline anisotropy energy can be increased through strain engineering by expanding the in-plane lattice parameter a. Altogether, we show that a quantitative description of the structural and magnetic properties of Mn2GaC is possible using PBE, which opens the way for further computational studies of these and related materials.
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Affiliation(s)
- Martin Dahlqvist
- Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83, Linköping, Sweden.
| | - Johanna Rosen
- Thin Film Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83, Linköping, Sweden.
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30
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Si L, Xiao W, Kaufmann J, Tomczak JM, Lu Y, Zhong Z, Held K. Topotactic Hydrogen in Nickelate Superconductors and Akin Infinite-Layer Oxides ABO_{2}. PHYSICAL REVIEW LETTERS 2020; 124:166402. [PMID: 32383925 DOI: 10.1103/physrevlett.124.166402] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 04/01/2020] [Indexed: 06/11/2023]
Abstract
Superconducting nickelates appear to be difficult to synthesize. Since the chemical reduction of ABO_{3} [rare earth (A), transition metal (B)] with CaH_{2} may result in both ABO_{2} and ABO_{2}H, we calculate the topotactic H binding energy by density functional theory (DFT). We find intercalating H to be energetically favorable for LaNiO_{2} but not for Sr-doped NdNiO_{2}. This has dramatic consequences for the electronic structure as determined by DFT+dynamical mean field theory: that of 3d^{9} LaNiO_{2} is similar to (doped) cuprates, 3d^{8} LaNiO_{2}H is a two-orbital Mott insulator. Topotactic H might hence explain why some nickelates are superconducting and others are not.
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Affiliation(s)
- Liang Si
- Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences, Ningbo 315201, China
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Wen Xiao
- Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences, Ningbo 315201, China
| | - Josef Kaufmann
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Jan M Tomczak
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
| | - Yi Lu
- Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - Zhicheng Zhong
- Key Laboratory of Magnetic Materials and Devices and Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering (NIMTE), Chinese Academy of Sciences, Ningbo 315201, China
- China Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Karsten Held
- Institute for Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria
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31
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Kumar S, Patrick CE, Edwards RS, Balakrishnan G, Lees MR, Staunton JB. Torque magnetometry study of the spin reorientation transition and temperature-dependent magnetocrystalline anisotropy in NdCo 5. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:255802. [PMID: 32249761 DOI: 10.1088/1361-648x/ab7ad6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present the results of torque magnetometry and magnetic susceptibility measurements to study in detail the spin reorientation transition (SRT) and magnetic anisotropy in the permanent magnet NdCo5. We further show simulations of the measurements using first-principles calculations based on density-functional theory and the disordered local moment picture of magnetism at finite temperatures. The good agreement between theory and experimental data leads to a detailed description of the physics underpinning the SRT. In particular we are able to resolve the magnetization of, and to reveal a canting between, the Nd and Co sublattices. The torque measurements carried out in the ac and ab planes near the easy direction allow us to estimate the anisotropy constants, K 1, K 2 and K 4 and their temperature dependences. Torque curves, τ(γ) recorded by varying the direction of a constant magnetic field in the crystallographic ac plane show a reversal in the polarity as the temperature is changed across the SRT (240 < T < 285 K). Within this domain, τ(γ) exhibits unusual features different to those observed above and below the transition. The single crystals of NdCo5 were grown using the optical floating zone technique.
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Affiliation(s)
- Santosh Kumar
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
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32
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Robarts HC, Millichamp TE, Lagos DA, Laverock J, Billington D, Duffy JA, O'Neill D, Giblin SR, Taylor JW, Kontrym-Sznajd G, Samsel-Czekała M, Bei H, Mu S, Samolyuk GD, Stocks GM, Dugdale SB. Extreme Fermi Surface Smearing in a Maximally Disordered Concentrated Solid Solution. PHYSICAL REVIEW LETTERS 2020; 124:046402. [PMID: 32058766 DOI: 10.1103/physrevlett.124.046402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 12/20/2019] [Indexed: 06/10/2023]
Abstract
We show that the Fermi surface can survive the presence of extreme compositional disorder in the equiatomic alloy Ni_{0.25}Fe_{0.25}Co_{0.25}Cr_{0.25}. Our high-resolution Compton scattering experiments reveal a Fermi surface which is smeared across a significant fraction of the Brillouin zone (up to 40% of 2π/a). The extent of this smearing and its variation on and between different sheets of the Fermi surface have been determined, and estimates of the electron mean free path and residual resistivity have been made by connecting this smearing with the coherence length of the quasiparticle states.
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Affiliation(s)
- Hannah C Robarts
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Thomas E Millichamp
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Daniel A Lagos
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - Jude Laverock
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | - David Billington
- Japan Synchrotron Radiation Research Institute, SPring-8, Sayo 679-5198, Japan
- School of Physics and Astronomy, Cardiff University, Queen's Building, The Parade, Cardiff CF24 3AA, United Kingdom
| | - Jonathan A Duffy
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Daniel O'Neill
- Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Sean R Giblin
- School of Physics and Astronomy, Cardiff University, Queen's Building, The Parade, Cardiff CF24 3AA, United Kingdom
| | - Jonathan W Taylor
- DMSC-European Spallation Source, Universitetsparken 1, Copenhagen 2100, Denmark
| | - Grazyna Kontrym-Sznajd
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wrocław 2, Poland
| | - Małgorzata Samsel-Czekała
- Institute of Low Temperature and Structure Research, Polish Academy of Sciences, PO Box 1410, 50-950 Wrocław 2, Poland
| | - Hongbin Bei
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Sai Mu
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - German D Samolyuk
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Malcolm Stocks
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Stephen B Dugdale
- H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
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33
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Wu Z, Zhang H, Lin J, Zhao J, Cheng X. Hydrogenated C3N: Variable-bandgap stable structures and induced antiferromagnetic properties. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2019.110471] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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34
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Liu Y, Wang K, Xiao H, Chen G, Wang Z, Hu T, Fan T, Ma L. Theoretical study of the mechanical properties of CrFeCoNiMox (0.1 ≤ x ≤ 0.3) alloys. RSC Adv 2020; 10:14080-14088. [PMID: 35498461 PMCID: PMC9051651 DOI: 10.1039/d0ra00111b] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 03/31/2020] [Indexed: 11/21/2022] Open
Abstract
Based on exact muffin-tin orbitals (EMTO) and coherent potential approximation (CPA), we investigate the effects of Mo content on the mechanical properties of CrFeCoNiMox (0.1 ≤ x ≤ 0.3) high-entropy alloys (HEAs) with a face-centered-cubic (fcc) crystal structure; relevant physical parameters are calculated as a function of Mo content. The results indicate that the theoretical predictions of lattice constant, elastic constants, shear modulus, and Young's modulus are in good agreement with the available experimental data, which proves the validity of the applied approach. CrFeCoNiMo0.26 HEA has better ductility and plasticity with respect to other HEAs with different Mo contents because it has the minimum elastic moduli and Vickers hardness, and has the maximum Pugh's ratio and anisotropy factors, etc. CrFeCoNiMo0.2 HEA has better plasticity compared with CrFeCoNiMo0.1 and CrFeCoNiMo0.3 HEAs due to its minimum energy factor and maximum dislocation width. Screw dislocation is more likely to nucleate in CrFeCoNiMox (0.1 ≤ x ≤ 0.3) HEAs than edge dislocation. The present studies are helpful to explore the excellent mechanical properties of CrFeCoNiMox (0.1 ≤ x ≤ 0.3) HEAs during experiments. There is a dramatic change of the elastic constants when Mo content increases from 0.26 to 0.28, indicating that the deformation resistance of CrFeCoNiMox (0.26 ≤ x ≤ 0.28) HEAs has changed greatly.![]()
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Affiliation(s)
- Yu Liu
- College of Materials Science and Engineering
- Hunan University
- Changsha
- P. R. China
| | - Kai Wang
- School of Mechatronics Engineering
- Foshan University
- Foshan
- P. R. China
| | - Hui Xiao
- School of Mechatronics Engineering
- Foshan University
- Foshan
- P. R. China
| | - Gang Chen
- College of Materials Science and Engineering
- Hunan University
- Changsha
- P. R. China
| | - Zhipeng Wang
- School of Material Science and Energy Engineering
- Foshan University
- Foshan
- P. R. China
| | - Te Hu
- School of Material Science and Energy Engineering
- Foshan University
- Foshan
- P. R. China
| | - Touwen Fan
- School of Material Science and Energy Engineering
- Foshan University
- Foshan
- P. R. China
| | - Li Ma
- Key Laboratory of New Electric Functional Materials of Guangxi Colleges and Universities
- Nanning Normal University
- Nanning
- P. R. China
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35
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Sun X, Zhang H, Li W, Ding X, Wang Y, Vitos L. Generalized Stacking Fault Energy of Al-Doped CrMnFeCoNi High-Entropy Alloy. NANOMATERIALS 2019; 10:nano10010059. [PMID: 31887990 PMCID: PMC7022399 DOI: 10.3390/nano10010059] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 12/23/2019] [Accepted: 12/25/2019] [Indexed: 11/16/2022]
Abstract
Using first-principles methods, we investigate the effect of Al on the generalized stacking fault energy of face-centered cubic (fcc) CrMnFeCoNi high-entropy alloy as a function of temperature. Upon Al addition or temperature increase, the intrinsic and extrinsic stacking fault energies increase, whereas the unstable stacking fault and unstable twinning fault energies decrease monotonously. The thermodynamic expression for the intrinsic stacking fault energy in combination with the theoretical Gibbs energy difference between the hexagonal close packed (hcp) and fcc lattices allows one to determine the so-called hcp-fcc interfacial energy. The results show that the interfacial energy is small and only weakly dependent on temperature and Al content. Two parameters are adopted to measure the nano-twinning ability of the present high-entropy alloys (HEAs). Both measures indicate that the twinability decreases with increasing temperature or Al content. The present study provides systematic theoretical plasticity parameters for modeling and designing high entropy alloys with specific mechanical properties.
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Affiliation(s)
- Xun Sun
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden; (X.S.); (W.L.); (L.V.)
- Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China;
| | - Hualei Zhang
- Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China;
- Correspondence:
| | - Wei Li
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden; (X.S.); (W.L.); (L.V.)
| | - Xiangdong Ding
- Frontier Institute of Science and Technology, State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China;
| | - Yunzhi Wang
- Department of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210, USA;
| | - Levente Vitos
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden; (X.S.); (W.L.); (L.V.)
- Division of Materials Theory, Department of Physics and Materials Science, Uppsala University, P.O. Box 516, SE-75120 Uppsala, Sweden
- Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, H-1525 Budapest, Hungary
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36
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Prediction and observation of an antiferromagnetic topological insulator. Nature 2019; 576:416-422. [PMID: 31853084 DOI: 10.1038/s41586-019-1840-9] [Citation(s) in RCA: 214] [Impact Index Per Article: 42.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 09/18/2019] [Indexed: 11/08/2022]
Abstract
Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics1, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic4 and electronic5 properties of these materials, restricting the observation of important effects to very low temperatures2,3. An intrinsic magnetic topological insulator-a stoichiometric well ordered magnetic compound-could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering that MnBi2Te4 shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ2 topological classification; ℤ2 = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling6-8 and axion electrodynamics9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3.
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37
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Huelmo CP, Denis PA. Unraveling the electromagnetic structure of the epitaxial graphene buffer layer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:435001. [PMID: 31269473 DOI: 10.1088/1361-648x/ab2ee2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We have employed density functional theory to study the structural, electronic and magnetic properties of the first all-carbon layer grown epitaxially on 6H-SiC(0 0 0 1). Using VDW-DF, M06-L, LSDA, LSDA+U, PBE and PBE-D2 methods we have performed a comparative study of the preferable magnetic configuration of the system. In this work, for the first time, we report a stable antiferromagnetic (AF) ordering in the buffer layer caused by the presence of silicon dangling bonds in the SiC top layer. This state is nearly degenerated with the ferromagnetic state with a magnetic moment equal to the number of silicon dangling bonds. A net magnetic moment of 0.55 µb per Si dangling bond was found for both states. However, only for the ferromagnetic state the carbon atoms of the buffer layer exhibited a magnetic moment. The magnetic configuration is much more stable than the non-polarized one and might explain SQUID results and spin transport experiments with epitaxial graphene. Furthermore, we found that, as previously observed experimentally, the buffer layer is a true semiconductor.
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Affiliation(s)
- C Pereyra Huelmo
- Facultad de Química, Computational Nanotechnology, DETEMA, UDELAR, CC 1157, 11800 Montevideo, Uruguay
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38
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Effects of Alloying Elements on the Stacking Fault Energies of Ni58Cr32Fe10 Alloys: A First-Principle Study. METALS 2019. [DOI: 10.3390/met9111163] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Ni58Cr32Fe10-based alloys, such as Alloy 690 and filler metal 52 (FM-52), suffer from ductility dip cracking (DDC). It is reported that decreasing the stacking fault energy (SFE) of these materials could improve the DDC resistance of Alloy 690. In this work, the effects of alloying elements on the stacking fault energies (SFEs) of Ni58Cr32Fe10 alloys were studied using first-principle calculations. In our simulations, 2 at.% of Ni is replaced by alloy element X (X=Al, Co, Cu, Hf, Mn, Nb, Ta, Ti, V, and W). At a finite temperature, the SFEs were divided into the magnetic entropy (SFEmag) and 0 K (SFE0) contributions. Potentially, the calculated results could be used in the design of high-performance Ni58Cr32Fe10-based alloys or filler materials.
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39
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Pourovskii LV. Electronic correlations in dense iron: from moderate pressure to Earth's core conditions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:373001. [PMID: 31167170 DOI: 10.1088/1361-648x/ab274f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We discuss the role of dynamical many-electron effects in the physics of iron and iron-rich solid alloys under applied pressure on the basis of recent ab initio studies employing the dynamical mean-field theory (DMFT). We review in detail two particularly interesting regimes: first, a moderate pressure range up to 60 GPa and, second, the ultra-high pressure of about 360 GPa expected inside the solid inner core of Earth. Electronic correlations in iron under the moderate pressure of several tens GPa are discussed in the first section. DMFT-based methods predict an enhancement of electronic correlations at the pressure-induced body-centered cubic α to hexagonal close-packed [Formula: see text] phase transition. In particular, the electronic effective mass, scattering rate and electron-electron contribution to the electrical resistivity undergo a step-wise increase at the transition point. One also finds a significant many-body correction to the [Formula: see text]-Fe equation of state, thus clarifying the origin of discrepancies between previous DFT studies and experiment. An electronic topological transition is predicted to be induced in [Formula: see text]-Fe by many-electron effects; its experimental signatures are analyzed. The next section focuses on the geophysically relevant pressure-temperature regime of the Earth's inner core (EIC) corresponding to the extreme pressure of 360 GPa combined with temperatures up to 6000 K. The three iron allotropes ([Formula: see text], [Formula: see text] and face-centered-cubic [Formula: see text]) previously proposed as possible stable phases at such conditions are found to exhibit qualitatively different many-electron effects as evidenced by a strongly non-Fermi-liquid metallic state of [Formula: see text]-Fe and an almost perfect Fermi liquid in the case of [Formula: see text]-Fe. A recent active discussion on the electronic state and transport properties of [Formula: see text]-Fe at the EIC conditions is reviewed in details. Estimations for the dynamical many-electron contribution to the relative phase stability are presented. We also discuss the impact of a Ni admixture, which is expected to be present in the core matter. We conclude by outlining some limitation of the present DMFT-based framework relevant for studies of iron-base systems as well as perspective directions for further development.
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Affiliation(s)
- Leonid V Pourovskii
- CPHT, CNRS, Ecole Polytechnique, IP Paris, F-91128 Palaiseau, France. Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France
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Patrick CE, Staunton JB. Crystal field coefficients for yttrium analogues of rare-earth/transition-metal magnets using density-functional theory in the projector-augmented wave formalism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:305901. [PMID: 30978708 DOI: 10.1088/1361-648x/ab18f3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We present a method of calculating crystal field coefficients of rare-earth/transition-metal (RE-TM) magnets within density-functional theory (DFT). The principal idea of the method is to calculate the crystal field potential of the yttrium analogue ('Y-analogue') of the RE-TM magnet, i.e. the material where the lanthanide elements have been substituted with yttrium. The advantage of dealing with Y-analogues is that the methodological and conceptual difficulties associated with treating the highly-localized 4f electrons in DFT are avoided, whilst the nominal valence electronic structure principally responsible for the crystal field is preserved. In order to correctly describe the crystal field potential in the core region of the atoms we use the projector-augmented wave formalism of DFT, which allows the reconstruction of the full charge density and electrostatic potential. The Y-analogue crystal field potentials are combined with radial 4f charge densities obtained in self-interaction-corrected calculations on the lanthanides to obtain crystal field coefficients. We demonstrate our method on a test set of ten materials comprising nine RE-TM magnets and elemental Tb. We show that the calculated easy directions of magnetization agree with experimental observations, including a correct description of the anisotropy within the basal plane of Tb and NdCo5. We further show that the Y-analogue calculations generally agree quantitatively with previous calculations using the open-core approximation to treat the 4f electrons, and argue that our simple approach may be useful for large-scale computational screening of new magnetic materials.
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Razumovskiy VI, Hahn C, Lukas M, Romaner L. Ab Initio Study of Elastic and Mechanical Properties in FeCrMn Alloys. MATERIALS 2019; 12:ma12071129. [PMID: 30959910 PMCID: PMC6480156 DOI: 10.3390/ma12071129] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 03/29/2019] [Accepted: 04/03/2019] [Indexed: 11/26/2022]
Abstract
Mechanical properties of FeCrMn-based steels are of major importance for practical applications. In this work, we investigate mechanical properties of disordered paramagnetic fcc FeCr10–16Mn12–32 alloys using density functional theory. The effects of composition and temperature changes on the magnetic state, elastic properties and stacking fault energies of the alloys are studied. Calculated dependencies of the lattice and elastic constants are used to evaluate the effect of the solid solution strengthening by Mn and Cr using a modified Labusch-Nabarro model and a model for concentrated alloys. The effect of Cr and Mn alloying on the stacking fault energies is calculated and discussed in connection to possible deformation mechanisms.
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Affiliation(s)
| | - Carola Hahn
- Materials Center Leoben Forschung GmbH (MCL), Roseggerstraße 12, 8700 Leoben, Austria.
| | - Marina Lukas
- Materials Center Leoben Forschung GmbH (MCL), Roseggerstraße 12, 8700 Leoben, Austria.
| | - Lorenz Romaner
- Materials Center Leoben Forschung GmbH (MCL), Roseggerstraße 12, 8700 Leoben, Austria.
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Xie R, Li W, Lu S, Song Y, Vitos L. Generalized stacking fault energy of carbon-alloyed paramagnetic [Formula: see text]-Fe. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:065703. [PMID: 30524044 DOI: 10.1088/1361-648x/aaf2fa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Generalized stacking fault energy (GSFE) is an important parameter for understanding the underlying physics governing the deformation mechanisms in face-centred cubic (fcc) materials. In the present work, we study the long-standing question regarding the influence of C on the GSFE in austenitic steels at paramagnetic state. We calculate the GSFE in both [Formula: see text]-Fe and Fe-C alloys using the exact muffin-tin orbitals method and the Vienna Ab initio Simulation Package. Our results show that the GSFE is increased by the presence of interstitial C, and the universal scaling law is used to verify the accuracy of the obtained stacking fault energies. The C-driven change of the GSFE is discussed considering the magnetic contributions. The effective energy barriers for stacking fault, twinning and slip formation are employed to disclose the C effect on the deformation modes, and we also demonstrate that the magnetic structures as a function of volume explain the effect of paramagnetism on the C-driven changes of the stacking fault energies as compared to the hypothetical non-magnetic case.
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Affiliation(s)
- Ruiwen Xie
- Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm SE-10044, Sweden
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Elastic Properties of FeCr20Ni8Xn (X = Mo, Nb, Ta, Ti, V, W and Zr) Austenitic Stainless Steels: A First Principles Study. METALS 2019. [DOI: 10.3390/met9020145] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Austenitic stainless steels suffer from intergranular corrosion and stress corrosion cracking when exposed to elevated temperature (500–800 °C). Under these environments, Cr-carbides and Cr-carbontrides precipitate at the grain boundaries, which results in the formation of Cr-depleted zone. In practice, alloying elements could be added into austenitic stainless steels to modify the precipitation processes. Besides the precipitation processes, the elastic properties of the iron matrix would be influenced. Using the exact muffin-tin orbitals (EMTO) method, the solute effects on the elastic properties of FeCr20Ni8 austenitic stainless steels were studied. Based on the simulated shear modulus (G) and bulk modulus (B), we proposed a design map for FeCr20Ni8 based alloys, aiming to provide a basis for the design of high-performance austenitic stainless steels.
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Buczek P, Thomas S, Marmodoro A, Buczek N, Zubizarreta X, Hoffmann M, Balashov T, Wulfhekel W, Zakeri K, Ernst A. Spin waves in disordered materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:423001. [PMID: 30182926 DOI: 10.1088/1361-648x/aadefb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present an efficient methodology to study spin waves in disordered materials. The approach is based on a Heisenberg model and enables calculations of magnon properties in spin systems with disorder of an arbitrary kind and concentration of impurities. Disorder effects are taken into account within two complementary approaches. Magnons in systems with substitutional (uncorrelated) disorder can be efficiently calculated within a single-site coherent potential approximation for the Heisenberg model. From the computation point of view the method is inexpensive and directly applicable to systems like alloys and doped materials. It is shown that it performs exceedingly well across all concentrations and wave vectors. Another way is the direct numerical simulation of large supercells using a configurational average over possible samples. This approach is applicable to systems with an arbitrary kind of disorder. The effective interaction between magnetic moments entering the Heisenberg model can be obtained from first-principles using a self-consistent Green function method within the density functional theory. Thus, our method can be viewed as an ab initio approach and can be used for calculations of magnons in real materials.
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Affiliation(s)
- Paweł Buczek
- Hochschule für Angewandte Wissenschaften Hamburg, Fakultät Technik und Informatik, Berliner Tor 7, 20099 Hamburg, Germany
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Wiktor J, Reshetnyak I, Strach M, Scarongella M, Buonsanti R, Pasquarello A. Sizable Excitonic Effects Undermining the Photocatalytic Efficiency of β-Cu 2V 2O 7. J Phys Chem Lett 2018; 9:5698-5703. [PMID: 30193068 DOI: 10.1021/acs.jpclett.8b02323] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Copper vanadates have been proposed as promising photoanodes for water-splitting photoelectrochemical cells, but their performance has recently been shown to be severely limited. To understand this behavior, we study the electronic structure and the optical properties of β-Cu2V2O7 both experimentally and computationally. The measured absorption spectrum shows an absorption peak at 1.5 eV followed by the onset of an apparent continuum at 2.26 eV, as generally found for this class of materials. We perform calculations within the framework of the QS GW̃ method and the Bethe-Salpeter equation while including effects of magnetic ordering, nuclear quantum motion, and thermal vibrations. We demonstrate the occurrence of two kinds of excitons with high binding energies upon optical excitation in β-Cu2V2O7, which account for the first absorption peak and the lower edge of the apparent continuum. The results are confirmed by photoluminescence measurements, where sub-band-gap emissions are found for both excitons. These results provide an explanation for the low photocatalytic efficiencies of copper vanadates, despite the favorable size of their optical band gaps.
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Affiliation(s)
- Julia Wiktor
- Chaire de Simulation à l'Echelle Atomique (CSEA) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Igor Reshetnyak
- Chaire de Simulation à l'Echelle Atomique (CSEA) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Michal Strach
- Laboratory of Nanochemistry for Energy (LNCE) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1951 Sion , Switzerland
| | - Mariateresa Scarongella
- Laboratory of Nanochemistry for Energy (LNCE) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1951 Sion , Switzerland
| | - Raffaella Buonsanti
- Laboratory of Nanochemistry for Energy (LNCE) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1951 Sion , Switzerland
| | - Alfredo Pasquarello
- Chaire de Simulation à l'Echelle Atomique (CSEA) , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
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Ikeda Y, Körmann F, Tanaka I, Neugebauer J. Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles. ENTROPY 2018; 20:e20090655. [PMID: 33265744 PMCID: PMC7513178 DOI: 10.3390/e20090655] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 08/28/2018] [Accepted: 08/29/2018] [Indexed: 11/16/2022]
Abstract
Medium and high entropy alloys (MEAs and HEAs) based on 3d transition metals, such as face-centered cubic (fcc) CrCoNi and CrMnFeCoNi alloys, reveal remarkable mechanical properties. The stacking fault energy (SFE) is one of the key ingredients that controls the underlying deformation mechanism and hence the mechanical performance of materials. Previous experiments and simulations have therefore been devoted to determining the SFEs of various MEAs and HEAs. The impact of local chemical environment in the vicinity of the stacking faults is, however, still not fully understood. In this work, we investigate the impact of the compositional fluctuations in the vicinity of stacking faults for two prototype fcc MEAs and HEAs, namely CrCoNi and CrMnFeCoNi by employing first-principles calculations. Depending on the chemical composition close to the stacking fault, the intrinsic SFEs vary in the range of more than 150 mJ/m 2 for both the alloys, which indicates the presence of a strong driving force to promote particular types of chemical segregations towards the intrinsic stacking faults in MEAs and HEAs. Furthermore, the dependence of the intrinsic SFEs on local chemical fluctuations reveals a highly non-linear behavior, resulting in a non-trivial interplay of local chemical fluctuations and SFEs. This sheds new light on the importance of controlling chemical fluctuations via tuning, e.g., the annealing condition to obtain the desired mechanical properties for MEAs and HEAs.
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Affiliation(s)
- Yuji Ikeda
- Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
- Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
- Correspondence:
| | - Fritz Körmann
- Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
- Materials Science and Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands
| | - Isao Tanaka
- Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan
- Center for Elements Strategy Initiative for Structure Materials (ESISM), Kyoto University, Kyoto 606-8501, Japan
- Center for Materials Research by Information Integration, National Institute for Materials Science (NIMS), Tsukuba 305-0047, Japan
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587, Japan
| | - Jörg Neugebauer
- Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf, Germany
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Dong Z, Schönecker S, Li W, Chen D, Vitos L. Thermal spin fluctuations in CoCrFeMnNi high entropy alloy. Sci Rep 2018; 8:12211. [PMID: 30111892 PMCID: PMC6093928 DOI: 10.1038/s41598-018-30732-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/09/2018] [Indexed: 11/09/2022] Open
Abstract
High entropy alloys based on 3d transition metals display rich and promising magnetic characteristics for various high-technology applications. Understanding their behavior at finite temperature is, however, limited by the incomplete experimental data for single-phase alloys. Here we use first-principles alloy theory to investigate the magnetic structure of polymorphic CoCrFeMnNi in the paramagnetic state by accounting for the longitudinal spin fluctuations (LSFs) as a function of temperature. In both face-centered cubic (fcc) and hexagonal close-packed (hcp) structures, the LSFs induce sizable magnetic moments for Co, Cr and Ni. The impact of LSFs is demonstrated on the phase stability, stacking fault energy and the fcc-hcp interfacial energy. The hcp phase is energetically preferable to the fcc one at cryogenic temperatures, which results in negative stacking fault energy at these conditions. With increasing temperature, the stacking fault energy increases, suppressing the formation of stacking faults and nano-twins. Our predictions are consistent with recent experimental findings.
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Affiliation(s)
- Zhihua Dong
- Applied Materials Physics, Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Stockholm, SE, 10044, Sweden.
| | - Stephan Schönecker
- Applied Materials Physics, Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Stockholm, SE, 10044, Sweden.
| | - Wei Li
- Applied Materials Physics, Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Stockholm, SE, 10044, Sweden
| | - Dengfu Chen
- College of Materials Science and Engineering, Chongqing University, Chongqing, 400030, P.R. China
| | - Levente Vitos
- Applied Materials Physics, Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Stockholm, SE, 10044, Sweden. .,Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE, 75121, Uppsala, Sweden. .,Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, H-1525, Budapest, Hungary.
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Patrick CE, Kumar S, Götze K, Pearce MJ, Singleton J, Rowlands G, Balakrishnan G, Lees MR, Goddard PA, Staunton JB. Field-induced canting of magnetic moments in GdCo 5 at finite temperature: first-principles calculations and high-field measurements. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:32LT01. [PMID: 29957599 DOI: 10.1088/1361-648x/aad029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We present calculations and experimental measurements of the temperature-dependent magnetization of a single crystal of GdCo5 in magnetic fields of order 60 T. At zero temperature the calculations, based on density-functional theory in the disordered-local-moment picture, predict a field-induced transition from an antiferromagnetic to a canted alignment of Gd and Co moments at 46.1 T. At higher temperatures the calculations find this critical field to increase along with the zero-field magnetization. The experimental measurements observe this transition to occur between 44-48 T at 1.4 K. Up to temperatures of at least 100 K, the experiments continue to observe the transition; however, at variance with the calculations, no strong temperature dependence of the critical field is apparent. We assign this difference to the inaccurate description of the zero-field magnetization of the calculations at low temperatures, due to the use of classical statistical mechanics. Correcting for this effect, we recover a consistent description of the high-field magnetization of GdCo5 from theory and experiment.
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Li X, Irving DL, Vitos L. First-principles investigation of the micromechanical properties of fcc-hcp polymorphic high-entropy alloys. Sci Rep 2018; 8:11196. [PMID: 30046064 PMCID: PMC6060180 DOI: 10.1038/s41598-018-29588-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/09/2018] [Indexed: 11/25/2022] Open
Abstract
High-entropy alloys offer a promising alternative in several high-technology applications concerning functional, safety and health aspects. Many of these new alloys compete with traditional structural materials in terms of mechanical characteristics. Understanding and controlling their properties are of the outmost importance in order to find the best single- or multiphase solutions for specific uses. Here, we employ first-principles alloy theory to address the micro-mechanical properties of five polymorphic high-entropy alloys in their face-centered cubic (fcc) and hexagonal close-packed (hcp) phases. Using the calculated elastic parameters, we analyze the mechanical stability, elastic anisotropy, and reveal a strong correlation between the polycrystalline moduli and the average valence electron concentration. We investigate the ideal shear strength of two selected alloys under shear loading and show that the hcp phase possesses more than two times larger intrinsic strength than that of the fcc phase. The derived half-width of the dislocation core predicts a smaller Peierls barrier in the fcc phase confirming its increased ductility compared to the hcp one. The present theoretical findings explain a series of important observations made on dual-phase alloys and provide an atomic-level knowledge for an intelligent design of further high-entropy materials.
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Affiliation(s)
- Xiaoqing Li
- Department of Materials Science and Engineering, KTH-Royal Institute of Technology, 10044, Stockholm, Sweden.
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA.
- Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest, H-1525, Hungary.
| | - Douglas L Irving
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, 27695, USA
| | - Levente Vitos
- Department of Materials Science and Engineering, KTH-Royal Institute of Technology, 10044, Stockholm, Sweden
- Research Institute for Solid State Physics and Optics, Wigner Research Center for Physics, P.O. Box 49, Budapest, H-1525, Hungary
- Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, SE-75120, Uppsala, Sweden
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Gimaev R, Zverev V, Spichkin Y, Tishin A, Miyanaga T. Peculiarities of the magnetocaloric effect in FeRh-based alloys in the vicinity of the first order magnetic phase transition. EPJ WEB OF CONFERENCES 2018. [DOI: 10.1051/epjconf/201818505008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Medical applications of magnetocaloric effect (MCE) require possibility for precision shift of a temperature of the magnetic phase transition at the same MCE value and minimize irreversibility. Thus, detail dynamic MCE investigation of such alloys with non-toxic biocompatible dopants need to be done. In present work, the giant magnetocaloric effect, which is observed in the whole family of Fe-Rh alloys, has been investigated in Pd-doped samples in slowly cycled magnetic fields of up to 1.8 T in magnitude for a range of temperatures, 250 K < T < 350 K. The shift of the ferromagnetic/antiferromagnetic transition temperature down towards room temperature and the decrease in the MCE have been observed in these alloys in comparison with a quasi-equiatomic FeRh alloy. The measurements have also shown an asymmetric behaviour of the first order magnetic phase transition with respect to whether the transition is traversed by heating from lower temperatures or cooling from above. These peculiarities have been explained in the framework of the ab-initio density functional theory-based disordered local moment theory of the MCE. The results have been compared with the those for the non-doped FeRh alloy. Thus features of the first order magnetic phase transition that these alloys have in common have been revealed which enable some predictions to be made appropriate for practical applications.
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