1
|
Wu M, Shi J, Sa N, Wu R, Deng T, Yang R, Zhang KHL, Han P, Wang HQ, Kang J. Ferromagnetic Insulating Ground-State Resolved in Mixed Protons and Oxygen Vacancies-Doped La 0.67Sr 0.33CoO 3 Thin Films via Ionic Liquid Gating. ACS APPLIED MATERIALS & INTERFACES 2024. [PMID: 38624095 DOI: 10.1021/acsami.4c00724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
The realization of ferromagnetic insulating ground state is a critical prerequisite for spintronic applications. By applying electric field-controlled ionic liquid gating (ILG) to stoichiometry La0.67Sr0.33CoO3 thin films, the doping of protons (H+) has been achieved for the first time. Furthermore, a hitherto-unreported ferromagnetic insulating phase with a remarkably high Tc up to 180 K has been observed which can be attributed to the doping of H+ and the formation of oxygen vacancies (VO). The chemical formula of the dual-ion migrated film has been identified as La2/3Sr1/3CoO8/3H2/3 based on combined Co L23-edge absorption spectra and configuration interaction cluster calculations, from which we are able to explain the ferromagnetic ground state in terms of the distinct magnetic moment contributions from Co ions with octahedral (Oh) and tetrahedral (Td) symmetries following antiparallel spin alignments. Further density functional theory calculations have been performed to verify the functionality of H+ as the transfer ion and the origin of the novel ferromagnetic insulating ground state. Our results provide a fundamental understanding of the ILG regulation mechanism and shed light on the manipulating of more functionalities in other correlated compounds through dual-ion manipulation.
Collapse
Affiliation(s)
- Meng Wu
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| | - Jueli Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Na Sa
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| | - Ruoyu Wu
- Department of Physics, Beijing Key Lab for Metamaterials and Devices, Capital Normal University, Beijing 100048, P.R. China
| | - Tielong Deng
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| | - Renqi Yang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| | - Kelvin H L Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China
| | - Peng Han
- Department of Physics, Beijing Key Lab for Metamaterials and Devices, Capital Normal University, Beijing 100048, P.R. China
| | - Hui-Qiong Wang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| | - Junyong Kang
- Fujian Key Laboratory of Semiconductor Materials and Applications, CI Center for OSED, and Department of Physics, Xiamen University, Xiamen 361005, P.R. China
| |
Collapse
|
2
|
Schmitt C, Rajan A, Beneke G, Kumar A, Sparmann T, Meer H, Bednarz B, Ramos R, Niño MA, Foerster M, Saitoh E, Kläui M. Mechanisms of Electrical Switching of Ultrathin CoO/Pt Bilayers. NANO LETTERS 2024; 24:1471-1476. [PMID: 38216142 PMCID: PMC10853954 DOI: 10.1021/acs.nanolett.3c02890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 12/21/2023] [Accepted: 12/21/2023] [Indexed: 01/14/2024]
Abstract
We study current-induced switching of the Néel vector in CoO/Pt bilayers to understand the underlying antiferromagnetic switching mechanism. Surprisingly, we find that for ultrathin CoO/Pt bilayers electrical pulses along the same path can lead to an increase or decrease of the spin Hall magnetoresistance signal, depending on the current density of the pulse. By comparing these results to XMLD-PEEM imaging of the antiferromagnetic domain structure before and after the application of current pulses, we reveal the details of the reorientation of the Néel vector in ultrathin CoO(4 nm). This allows us to understand how opposite resistance changes can result from a thermomagnetoelastic switching mechanism. Importantly, our spatially resolved imaging shows that regions where the current pulses are applied and regions further away exhibit different switched spin structures, which can be explained by a spin-orbit torque-based switching mechanism that can dominate in very thin films.
Collapse
Affiliation(s)
- Christin Schmitt
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Adithya Rajan
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Grischa Beneke
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Aditya Kumar
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Tobias Sparmann
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Hendrik Meer
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Beatrice Bednarz
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Rafael Ramos
- WPI-Advanced
Institute for Materials Research, Tohoku
University, Sendai 980-8577, Japan
| | - Miguel Angel Niño
- ALBA
Synchrotron Light Facility, 08290 Cerdanyola del Valles (Barcelona), Spain
| | - Michael Foerster
- ALBA
Synchrotron Light Facility, 08290 Cerdanyola del Valles (Barcelona), Spain
| | - Eiji Saitoh
- WPI-Advanced
Institute for Materials Research, Tohoku
University, Sendai 980-8577, Japan
- Institute
for Materials Research, Tohoku University, Sendai 980-8577, Japan
- The
Institute of AI and Beyond, The University
of Tokyo, Tokyo 113-8656, Japan
- Center
for
Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department
of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Mathias Kläui
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
- Graduate
School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| |
Collapse
|
3
|
Mandziak A, de la Figuera J, Quesada A, Berja A, Granados-Miralles C, Prieto JE, Aballe L, Foerster M, Nino MA, Nita P. Effect of Ni substitution on the antiferromagnetic domains of cobalt oxide. Ultramicroscopy 2023; 253:113795. [PMID: 37399618 DOI: 10.1016/j.ultramic.2023.113795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 04/20/2023] [Accepted: 06/11/2023] [Indexed: 07/05/2023]
Abstract
We present a spatially resolved X-ray magnetic linear dichroism study of high quality micron-sized mixed nickel-cobalt oxide (NCO) crystals. NixCo1-xO was prepared in-situ by high-temperature oxygen-assisted molecular beam epitaxy on a Ru(0001) single crystal substrate. To check the effect of incorporating Ni into the cobalt oxide films, three different compositions were prepared. The element-specific XMLD measurements reveal strong antiferromagnetic contrast at room temperature and magnetic domains up to one micron in size, reflecting the high structural quality of the NCO islands. By means of vectorial magnetometry, the antiferromagnetic spin axis orientation of the domains was determined with nanometer spatial resolution, and found to depend on the stoichiometry of the prepared crystals.
Collapse
Affiliation(s)
- Anna Mandziak
- Solaris Synchrotron, Czerwone Maki 98, 30-392 Cracow, Poland.
| | | | - Adrian Quesada
- Instituto de Cerámica y Vidrio (CSIC), Madrid E-28049, Spain
| | - Alba Berja
- Instituto de Cerámica y Vidrio (CSIC), Madrid E-28049, Spain
| | | | | | - Lucia Aballe
- Alba Synchrotron Light Facility, CELLS, Barcelona E-08290, Spain
| | - Michael Foerster
- Alba Synchrotron Light Facility, CELLS, Barcelona E-08290, Spain
| | | | - Pawel Nita
- Solaris Synchrotron, Czerwone Maki 98, 30-392 Cracow, Poland; Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, ul. prof. Stanisława Łojasiewicza 11, 30-348 Cracow, Poland
| |
Collapse
|
4
|
Kuo CY, Liou YD, Hu Z, Liao SC, Tsai HM, Fu HW, Hua CY, Chen YC, Lin HJ, Tanaka A, Chen CT, Yang JC, Chang CF. Photonic-Crafting of Non-Volatile and Rewritable Antiferromagnetic Spin Textures with Drastic Difference in Electrical Conductivity. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2200610. [PMID: 35312103 DOI: 10.1002/adma.202200610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/15/2022] [Indexed: 06/14/2023]
Abstract
Antiferromagnetic spintronics is an emerging field of non-volatile data storage and information processing. The zero net magnetization and zero stray fields of antiferromagnetic materials eliminate interference between neighbor units, leading to high-density memory integrations. However, this invisible magnetic character at the same time also poses a great challenge in controlling and detecting magnetic states in antiferromagnets. Here, two antiferromagnetic spin states close in energy in strained BiFeO3 thin films at room temperature are discovered. It can be reversibly switched between these two non-volatile antiferromagnetic states by a moderate magnetic field and a non-contact optical approach. Importantly, the conductivity of the areas with each antiferromagnetic textures is drastically different. It is conclusively demonstrated the capability of optical writing and electrical reading of these newly discovered bistable antiferromagnetic states in the BiFeO3 thin films.
Collapse
Affiliation(s)
- Chang-Yang Kuo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Yi-De Liou
- Department of Physics, National Cheng Kung University, Tainan, 70101, Taiwan
- Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan, 70101, Taiwan
| | - Zhiwei Hu
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, Dresden, 01187, Germany
| | - Sheng-Chieh Liao
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, Dresden, 01187, Germany
| | - Huang-Ming Tsai
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Huang-Wen Fu
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Chih-Yu Hua
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Yi-Chun Chen
- Department of Physics, National Cheng Kung University, Tainan, 70101, Taiwan
- Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan, 70101, Taiwan
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Arata Tanaka
- Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, 739-8530, Japan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Jan-Chi Yang
- Department of Physics, National Cheng Kung University, Tainan, 70101, Taiwan
- Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan, 70101, Taiwan
| | - Chun-Fu Chang
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, Dresden, 01187, Germany
| |
Collapse
|
5
|
Zhong X, Oubla M, Wang X, Huang Y, Zeng H, Wang S, Liu K, Zhou J, He L, Zhong H, Alonso-Vante N, Wang CW, Wu WB, Lin HJ, Chen CT, Hu Z, Huang Y, Ma J. Boosting oxygen reduction activity and enhancing stability through structural transformation of layered lithium manganese oxide. Nat Commun 2021; 12:3136. [PMID: 34035291 PMCID: PMC8149866 DOI: 10.1038/s41467-021-23430-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 04/28/2021] [Indexed: 11/30/2022] Open
Abstract
Structural degradation in manganese oxides leads to unstable electrocatalytic activity during long-term cycles. Herein, we overcome this obstacle by using proton exchange on well-defined layered Li2MnO3 with an O3-type structure to construct protonated Li2-xHxMnO3-n with a P3-type structure. The protonated catalyst exhibits high oxygen reduction reaction activity and excellent stability compared to previously reported cost-effective Mn-based oxides. Configuration interaction and density functional theory calculations indicate that Li2-xHxMnO3-n has fewer unstable O 2p holes with a Mn3.7+ valence state and a reduced interlayer distance, originating from the replacement of Li by H. The former is responsible for the structural stability, while the latter is responsible for the high transport property favorable for boosting activity. The optimization of both charge states to reduce unstable O 2p holes and crystalline structure to reduce the reaction pathway is an effective strategy for the rational design of electrocatalysts, with a likely extension to a broad variety of layered alkali-containing metal oxides.
Collapse
Affiliation(s)
- Xuepeng Zhong
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China
| | - M'hamed Oubla
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China
| | - Xiao Wang
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
| | - Yangyang Huang
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China
| | - Huiyan Zeng
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China
| | - Shaofei Wang
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organization, Kirrawee DC, NSW, Australia
| | - Kun Liu
- Center for Alloy Innovation and Design, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China
| | - Jian Zhou
- Center for Alloy Innovation and Design, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China
| | - Lunhua He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Songshan Lake Materials Laboratory, Dongguan, China
- Spallation Neutron Source Science Center, Dongguan, China
| | - Haihong Zhong
- IC2MP, UMR-CNRS 7285, University of Poitiers, Poitiers, France
| | | | - Chin-Wei Wang
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Wen-Bin Wu
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
| | - Yunhui Huang
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China.
| | - Jiwei Ma
- Shanghai Key Laboratory for R&D and Application of Metallic Functional Materials, Institute of New Energy for Vehicles, School of Materials Science and Engineering, Tongji University, Shanghai, China.
| |
Collapse
|
6
|
Amorphization-induced surface electronic states modulation of cobaltous oxide nanosheets for lithium-sulfur batteries. Nat Commun 2021; 12:3102. [PMID: 34035271 PMCID: PMC8149689 DOI: 10.1038/s41467-021-23349-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 04/16/2021] [Indexed: 11/25/2022] Open
Abstract
Lithium-sulfur batteries show great potential to achieve high-energy-density storage, but their long-term stability is still limited due to the shuttle effect caused by the dissolution of polysulfides into electrolyte. Herein, we report a strategy of significantly improving the polysulfides adsorption capability of cobaltous oxide by amorphization-induced surface electronic states modulation. The amorphous cobaltous oxide nanosheets as the cathode additives for lithium-sulfur batteries demonstrates the rate capability and cycling stability with an initial capacity of 1248.2 mAh g-1 at 1 C and a substantial capacity retention of 1037.3 mAh g-1 after 500 cycles. X-ray absorption spectroscopy analysis reveal that the coordination structures and symmetry of ligand field around Co atoms of cobaltous oxide nanosheets are notably changed after amorphization. Moreover, DFT studies further indicate that amorphization-induced re-distribution of d orbital makes more electrons occupy high energy level, thereby resulting in a high binding energy with polysulfides for favorable adsorption. Regulating the adsorption behaviour of the polysulfide species is the key to achieving highly stable Li-S batteries. Here, the authors show that amorphization-induced redistribution of d orbitals enable CoO to be a favourable candidate for polysulfide adsorption and conversion.
Collapse
|
7
|
Elnaggar H, Haverkort MW, Hamed MH, Dhesi SS, de Groot FMF. Tensor description of X-ray magnetic dichroism at the Fe L 2,3-edges of Fe 3O 4. JOURNAL OF SYNCHROTRON RADIATION 2021; 28:247-258. [PMID: 33399575 PMCID: PMC7842224 DOI: 10.1107/s1600577520015027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/11/2020] [Indexed: 05/27/2023]
Abstract
A procedure to build the optical conductivity tensor that describes the full magneto-optical response of the system from experimental measurements is presented. Applied to the Fe L2,3-edge of a 38.85 nm Fe3O4/SrTiO3 (001) thin-film, it is shown that the computed polarization dependence using the conductivity tensor is in excellent agreement with that experimentally measured. Furthermore, the magnetic field angular dependence is discussed using a set of fundamental spectra expanded on spherical harmonics. It is shown that the convergence of this expansion depends on the details of the ground state of the system in question and in particular on the valence-state spin-orbit coupling. While a cubic expansion up to the third order explains the angular-dependent X-ray magnetic linear dichroism of Fe3+ well, higher-order terms are required for Fe2+ when the orbital moment is not quenched.
Collapse
Affiliation(s)
- Hebatalla Elnaggar
- Debye Institute for Nanomaterials Science, Utrecht University, 99 Universiteitsweg, Utrecht 3584 CG, The Netherlands
| | - Maurits W. Haverkort
- Institute of Theoretical Physics, Heidelberg University, 19 Philosophenweg, Heidelberg 69120, Germany
| | - Mai Hussein Hamed
- Jülich Centre for Neutron Science, Forschungszentrum Juelich GmbH, Jülich 52425, Germany
- Faculty of Science, Helwan University, Cairo 11795, Egypt
| | - Sarnjeet S. Dhesi
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OC11 0DE, United Kingdom
| | - Frank M. F. de Groot
- Debye Institute for Nanomaterials Science, Utrecht University, 99 Universiteitsweg, Utrecht 3584 CG, The Netherlands
| |
Collapse
|
8
|
Baldrati L, Schmitt C, Gomonay O, Lebrun R, Ramos R, Saitoh E, Sinova J, Kläui M. Efficient Spin Torques in Antiferromagnetic CoO/Pt Quantified by Comparing Field- and Current-Induced Switching. PHYSICAL REVIEW LETTERS 2020; 125:077201. [PMID: 32857543 DOI: 10.1103/physrevlett.125.077201] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 07/02/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of 4×10^{-11} T A^{-1} m^{2}. The Néel vector final state (n⊥j) is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.
Collapse
Affiliation(s)
- L Baldrati
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - C Schmitt
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - O Gomonay
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - R Lebrun
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Unité Mixte de Physique CNRS, Thales, Université Paris-Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - R Ramos
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - E Saitoh
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - J Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Institute of Physics, Academy of Sciences of the Czech Republic, Praha 11720, Czech Republic
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - M Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| |
Collapse
|
9
|
Liu H, Chaloupka J, Khaliullin G. Kitaev Spin Liquid in 3d Transition Metal Compounds. PHYSICAL REVIEW LETTERS 2020; 125:047201. [PMID: 32794780 DOI: 10.1103/physrevlett.125.047201] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Accepted: 07/02/2020] [Indexed: 06/11/2023]
Abstract
We study the exchange interactions and resulting magnetic phases in the honeycomb cobaltates. For a broad range of trigonal crystal fields acting on Co^{2+} ions, the low-energy pseudospin-1/2 Hamiltonian is dominated by bond-dependent Ising couplings that constitute the Kitaev model. The non-Kitaev terms nearly vanish at small values of trigonal field Δ, resulting in spin liquid ground state. Considering Na_{3}Co_{2}SbO_{6} as an example, we find that this compound is proximate to a Kitaev spin liquid phase, and can be driven into it by slightly reducing Δ by ∼20 meV, e.g., via strain or pressure control. We argue that, due to the more localized nature of the magnetic electrons in 3d compounds, cobaltates offer the most promising search area for Kitaev model physics.
Collapse
Affiliation(s)
- Huimei Liu
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Jiří Chaloupka
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, Brno 61137, Czech Republic
- Central European Institute of Technology, Masaryk University, Kamenice 753/5, Brno 62500, Czech Republic
| | - Giniyat Khaliullin
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| |
Collapse
|
10
|
Choi WH, Moon BC, Park DG, Choi JW, Kim K, Shin J, Kim MG, Choi KM, Kang JK. Autogenous Production and Stabilization of Highly Loaded Sub-Nanometric Particles within Multishell Hollow Metal-Organic Frameworks and Their Utilization for High Performance in Li-O 2 Batteries. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2000283. [PMID: 32382491 PMCID: PMC7201254 DOI: 10.1002/advs.202000283] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/21/2020] [Accepted: 02/24/2020] [Indexed: 05/22/2023]
Abstract
Sub-nanometric particles (SNPs) of atomic cluster sizes have shown great promise in many fields such as full atom-to-atom utilization, but their precise production and stabilization at high mass loadings remain a great challenge. As a solution to overcome this challenge, a strategy allowing synthesis and preservation of SNPs at high mass loadings within multishell hollow metal-organic frameworks (MOFs) is demonstrated. First, alternating water-decomposable and water-stable MOFs are stacked in succession to build multilayer MOFs. Next, using controlled hydrogen bonding affinity, isolated water molecules are selectively sieved through the hydrophobic nanocages of water-stable MOFs and transferred one by one to water-decomposable MOFs. The transmission of water molecules via controlled hydrogen bonding affinity through the water-stable MOF layers is a key step to realize SNPs from various types of alternating water-decomposable and water-stable layers. This process transforms multilayer MOFs into SNP-embedded multishell hollow MOFs. Additionally, the multishell stabilizes SNPs by π-backbonding allowing high conductivity to be achieved via the hopping mechanism, and hollow interspaces minimize transport resistance. These features, as demonstrated using SNP-embedded multishell hollow MOFs with up to five shells, lead to high electrochemical performances including high volumetric capacities and low overpotentials in Li-O2 batteries.
Collapse
Affiliation(s)
- Won Ho Choi
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Byeong Cheul Moon
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Dong Gyu Park
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Jae Won Choi
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Keon‐Han Kim
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Jae‐Sun Shin
- Department of ChemistryKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| | - Min Gyu Kim
- Pohang Accelerator Laboratory (PAL)Korea Pohang University of Science and Technology77 Cheongam‐ro, Namg‐guPohang37673Republic of Korea
| | - Kyung Min Choi
- Department of Chemical and Biological EngineeringSookmyung Women's UniversityCheongpa‐ro 47‐gil 100, Yongsan‐guSeoul04310Republic of Korea
| | - Jeung Ku Kang
- Department of Materials Science and Engineering and NanoCentury KAIST InstituteKorea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
- Graduate School of EnergyEnvironment Water and Sustainability (EEWS)Korea Advanced Institute of Science and Technology (KAIST)291 Daehak‐ro, Yuseong‐guDaejeon34141Republic of Korea
| |
Collapse
|
11
|
Zhou J, Zhang L, Huang YC, Dong CL, Lin HJ, Chen CT, Tjeng LH, Hu Z. Voltage- and time-dependent valence state transition in cobalt oxide catalysts during the oxygen evolution reaction. Nat Commun 2020; 11:1984. [PMID: 32332788 PMCID: PMC7181785 DOI: 10.1038/s41467-020-15925-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 04/01/2020] [Indexed: 12/31/2022] Open
Abstract
The ability to determine the electronic structure of catalysts during electrochemical reactions is highly important for identification of the active sites and the reaction mechanism. Here we successfully applied soft X-ray spectroscopy to follow in operando the valence and spin state of the Co ions in Li2Co2O4 under oxygen evolution reaction (OER) conditions. We have observed that a substantial fraction of the Co ions undergo a voltage-dependent and time-dependent valence state transition from Co3+ to Co4+ accompanied by spontaneous delithiation, whereas the edge-shared Co-O network and spin state of the Co ions remain unchanged. Density functional theory calculations indicate that the highly oxidized Co4+ site, rather than the Co3+ site or the oxygen vacancy site, is mainly responsible for the high OER activity.
Collapse
Affiliation(s)
- Jing Zhou
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China
| | - Linjuan Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Yu-Cheng Huang
- Department of Physics, Tamkang University, 151 Yingzhuan Road, New Taipei City, 25137, Taiwan
| | - Chung-Li Dong
- Department of Physics, Tamkang University, 151 Yingzhuan Road, New Taipei City, 25137, Taiwan
| | - Hong-Ji Lin
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu, 30076, Taiwan
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187, Dresden, Germany.
| |
Collapse
|
12
|
Ha TD, Yen M, Lai YH, Kuo CY, Chen CT, Tanaka A, Tsai LZ, Zhao YF, Duan CG, Lee SF, Chang CF, Juang JY, Chu YH. Mechanically tunable exchange coupling of Co/CoO bilayers on flexible muscovite substrates. NANOSCALE 2020; 12:3284-3291. [PMID: 31971196 DOI: 10.1039/c9nr08810e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The employment of flexible muscovite substrates has given us the feasibility of applying strain to heterostructures dynamically by mechanical bending. In this study, this novel approach is utilized to investigate strain effects on the exchange coupling in ferromagnetic Co and anti-ferromagnetic CoO (Co/CoO) bilayers. Two different Co/CoO bilayer heterostructures were grown on muscovite substrates by oxide molecular beam epitaxy, with the CoO layer being purely (111)- and (100)-oriented. The strain-dependent exchange coupling effect can only be observed on Co/CoO(100)/mica but not on Co/CoO(111)/mica. The origin of this phenomenon is attributed to the anisotropic spin re-orientation induced by mechanical bending. The strain-dependent magnetic anisotropy of the bilayers determined by anisotropic magnetoresistance measurements confirms this conjecture. This study elucidates the fundamental understanding of how magnetic exchange coupling can be tuned by externally applied strain via mechanical bending and, hence, provides a novel approach for implementing flexible spintronic devices.
Collapse
Affiliation(s)
- Thai Duy Ha
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan. and Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Min Yen
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yu-Hong Lai
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Chang-Yang Kuo
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany and National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Chien-Te Chen
- National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan
| | - Arata Tanaka
- Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan
| | - Li-Zai Tsai
- Insitute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Feng Zhao
- Department of Electronic Engineering, East China Normal University, Shanghai, China
| | - Chun-Gang Duan
- Department of Electronic Engineering, East China Normal University, Shanghai, China
| | - Shang-Fan Lee
- Insitute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - Chun-Fu Chang
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, Dresden 01187, Germany
| | - Jenh-Yih Juang
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan.
| | - Ying-Hao Chu
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan. and Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan and Insitute of Physics, Academia Sinica, Taipei 11529, Taiwan
| |
Collapse
|
13
|
Miedema PS, Thielemann-Kühn N, Calafell IA, Schüßler-Langeheine C, Beye M. Strain analysis from M-edge resonant inelastic X-ray scattering of nickel oxide films. Phys Chem Chem Phys 2019; 21:21596-21602. [PMID: 31538993 DOI: 10.1039/c9cp03593a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Electronic structure modifications due to strain are an effective method for tailoring nano-scale functional materials. Demonstrated on nickel oxide (NiO) thin films, Resonant Inelastic X-ray Scattering (RIXS) at the transition-metal M2,3-edge is shown to be a powerful tool for measuring the electronic structure modification due to strain in the near-surface region. Analyses from the M2,3-edge RIXS in comparison with dedicated crystal field multiplet calculations show distortions in 40 nm NiO grown on a magnesium oxide (MgO) substrate (NiO/MgO) similar to those caused by surface relaxation of bulk NiO. The films of 20 and 10 nm NiO/MgO show slightly larger differences from bulk NiO. Quantitatively, the NiO/MgO samples all are distorted from perfect octahedral (Oh) symmetry with a tetragonal parameter Ds of about -0.1 eV, very close to the Ds distortion from octahedral (Oh) symmetry parameter of -0.11 eV obtained for the surface-near region from a bulk NiO crystal. Comparing the spectra of a 20 nm film of NiO grown on a 20 nm magnetite (Fe3O4) film on a MgO substrate (NiO/Fe3O4/MgO) with the calculated multiplet analyses, the distortion parameter Ds appears to be closer to zero, showing that the surface-near region of this templated film is less distorted from Oh symmetry than the surface-near region in bulk NiO. Finally, the potential of M2,3-edge RIXS for other investigations of strain on electronic structure is discussed.
Collapse
Affiliation(s)
- P S Miedema
- Deutsches Elektronen Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
| | - N Thielemann-Kühn
- Institute Methods and Instrumentation for Synchrotron Radiation Research (FG-ISRR), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany and Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
| | - I Alonso Calafell
- Institute Methods and Instrumentation for Synchrotron Radiation Research (FG-ISRR), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - C Schüßler-Langeheine
- Institute Methods and Instrumentation for Synchrotron Radiation Research (FG-ISRR), Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - M Beye
- Deutsches Elektronen Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany.
| |
Collapse
|
14
|
Tuning the Néel temperature in an antiferromagnet: the case of Ni xCo 1-xO microstructures. Sci Rep 2019; 9:13584. [PMID: 31537821 PMCID: PMC6753089 DOI: 10.1038/s41598-019-49642-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 08/27/2019] [Indexed: 11/08/2022] Open
Abstract
We show that it is possible to tune the Néel temperature of nickel(II)-cobalt(II) oxide films by changing the Ni to Co ratio. We grow single crystalline micrometric triangular islands with tens of nanometers thickness on a Ru(0001) substrate using high temperature oxygen-assisted molecular beam epitaxy. Composition is controlled by adjusting the deposition rates of Co and Ni. The morphology, shape, crystal structure and composition are determined by low-energy electron microscopy and diffraction, and synchrotron-based x-ray absorption spectromicroscopy. The antiferromagnetic order is observed by x-ray magnetic linear dichroism. Antiferromagnetic domains up to micrometer width are observed.
Collapse
|
15
|
Lee S, Lee AT, Georgescu AB, Fabbris G, Han MG, Zhu Y, Freeland JW, Disa AS, Jia Y, Dean MPM, Walker FJ, Ismail-Beigi S, Ahn CH. Strong Orbital Polarization in a Cobaltate-Titanate Oxide Heterostructure. PHYSICAL REVIEW LETTERS 2019; 123:117201. [PMID: 31573260 DOI: 10.1103/physrevlett.123.117201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 06/21/2019] [Indexed: 06/10/2023]
Abstract
Through a combination of experimental measurements and theoretical modeling, we describe a strongly orbital-polarized insulating ground state in an (LaTiO_{3})_{2}/(LaCoO_{3})_{2} oxide heterostructure. X-ray absorption spectra and ab initio calculations show that an electron is transferred from the titanate to the cobaltate layers. The charge transfer, accompanied by a large octahedral distortion, induces a substantial orbital polarization in the cobaltate layer of a size unattainable via epitaxial strain alone. The asymmetry between in-plane and out-of-plane orbital occupancies in the high-spin cobaltate layer is predicted by theory and observed through x-ray linear dichroism experiments. Manipulating orbital configurations using interfacial coupling within heterostructures promises exciting ground-state engineering for realizing new emergent electronic phases in metal oxide superlattices.
Collapse
Affiliation(s)
- Sangjae Lee
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Alex Taekyung Lee
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Alexandru B Georgescu
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
| | - Gilberto Fabbris
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Myung-Geun Han
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - John W Freeland
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Ankit S Disa
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Yichen Jia
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Mark P M Dean
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Frederick J Walker
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Sohrab Ismail-Beigi
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
| | - Charles H Ahn
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520, USA
| |
Collapse
|
16
|
Complex strain evolution of polar and magnetic order in multiferroic BiFeO 3 thin films. Nat Commun 2018; 9:3764. [PMID: 30242162 PMCID: PMC6155110 DOI: 10.1038/s41467-018-06190-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 08/20/2018] [Indexed: 11/08/2022] Open
Abstract
Electric-field control of magnetism requires deterministic control of the magnetic order and understanding of the magnetoelectric coupling in multiferroics like BiFeO3 and EuTiO3. Despite this critical need, there are few studies on the strain evolution of magnetic order in BiFeO3 films. Here, in (110)-oriented BiFeO3 films, we reveal that while the polarization structure remains relatively unaffected, strain can continuously tune the orientation of the antiferromagnetic-spin axis across a wide angular space, resulting in an unexpected deviation of the classical perpendicular relationship between the antiferromagnetic axis and the polarization. Calculations suggest that this evolution arises from a competition between the Dzyaloshinskii-Moriya interaction and single-ion anisotropy wherein the former dominates at small strains and the two are comparable at large strains. Finally, strong coupling between the BiFeO3 and the ferromagnet Co0.9Fe0.1 exists such that the magnetic anisotropy of the ferromagnet can be effectively controlled by engineering the orientation of the antiferromagnetic-spin axis.
Collapse
|
17
|
Sundermann M, Yavaş H, Chen K, Kim DJ, Fisk Z, Kasinathan D, Haverkort MW, Thalmeier P, Severing A, Tjeng LH. 4f Crystal Field Ground State of the Strongly Correlated Topological Insulator SmB_{6}. PHYSICAL REVIEW LETTERS 2018; 120:016402. [PMID: 29350947 DOI: 10.1103/physrevlett.120.016402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/25/2017] [Indexed: 06/07/2023]
Abstract
We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5} J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far.
Collapse
Affiliation(s)
- M Sundermann
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - H Yavaş
- PETRA III, Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany
| | - K Chen
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
| | - D J Kim
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Z Fisk
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - D Kasinathan
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - M W Haverkort
- Institute for Theoretical Physics, Heidelberg University, Philosophenweg 19, 69120 Heidelberg, Germany
| | - P Thalmeier
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - A Severing
- Institute of Physics II, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| |
Collapse
|
18
|
Kuświk P, Gastelois PL, Głowiński H, Przybylski M, Kirschner J. Impact of orthogonal exchange coupling on magnetic anisotropy in antiferromagnetic oxides/ferromagnetic systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:425001. [PMID: 27589202 DOI: 10.1088/0953-8984/28/42/425001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The influence of interface exchange coupling on magnetic anisotropy in the antiferromagnetic oxide/Ni system is investigated. We show how interfacial exchange coupling can be employed not only to pin the magnetization of the ferromagnetic layer but also to support magnetic anisotropy to orient the easy magnetization axis perpendicular to the film plane. The fact that this effect is only observed below the Néel temperature of all investigated antiferromagnetic oxides with significantly different magnetocrystalline anisotropies gives evidence that antiferromagnetic ordering is a source of the additional contribution to the perpendicular effective magnetic anisotropy.
Collapse
Affiliation(s)
- Piotr Kuświk
- Institute of Molecular Physics, Polish Academy of Sciences, 60179 Poznań, Poland. Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | | | | | | | | |
Collapse
|
19
|
Abstract
The strong coupling between antiferromagnetism and ferroelectricity at room temperature found in BiFeO3 generates high expectations for the design and development of technological devices with novel functionalities. However, the multi-domain nature of the material tends to nullify the properties of interest and complicates the thorough understanding of the mechanisms that are responsible for those properties. Here we report the realization of a BiFeO3 material in thin film form with single-domain behaviour in both its magnetism and ferroelectricity: the entire film shows its antiferromagnetic axis aligned along the crystallographic b axis and its ferroelectric polarization along the c axis. With this we are able to reveal that the canted ferromagnetic moment due to the Dzyaloshinskii–Moriya interaction is parallel to the a axis. Furthermore, by fabricating a Co/BiFeO3 heterostructure, we demonstrate that the ferromagnetic moment of the Co film does couple directly to the canted moment of BiFeO3. The coupling of ferroelectric and antiferromagnetic order in BiFeO3 makes it appealing for applications however the presence of domain structure acts to undermine this potential. Here, the authors demonstrate BiFeO3 thin films with a single domain of electrical polarization and canted antiferromagnetic order.
Collapse
|
20
|
Haw SC, Lee JM, Chen SA, Lu KT, Lee MT, Pi TW, Lee CH, Hu Z, Chen JM. Influence of Fe substitution on the Jahn-Teller distortion and orbital anisotropy in orthorhombic Y(Mn1-xFex)O3 epitaxial films. Dalton Trans 2016; 45:12393-9. [PMID: 27430045 DOI: 10.1039/c6dt01633b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multiferroic YMn1-xFexO3(020) (x = 0.125, 0.25, 0.50) epitaxial thin films with an orthorhombic structure (space group Pbnm) were prepared on a YAlO3(010) substrate by pulsed-laser deposition. Upon Fe substitution, the b-axis was clearly shortened, whereas the a- and c-axes were slightly lengthened based on XRD analysis. To understand the influence of orbital polarization and the Jahn-Teller effect of Mn(3+) on Fe substitution and also the local octahedral-site distortion of Fe(3+) in an environment of Jahn-Teller-active Mn(3+) ions in YMn1-xFexO3 films, we measured the polarization-dependent X-ray absorption spectra at the Mn-L2,3 and Fe-L2,3 edges, and also simulated the experimental spectra using configuration-interaction multiplet calculations. Although Δeg for the Mn(3+) ion decreased from 0.9 eV in pure YMnO3 to 0.6 eV in the half-Fe-substituted sample, a single eg electron was still strongly constrained to the d3y(2)-r(2) orbital for all the Fe concentrations tested. The largest Δeg, 0.5 eV, for the Fe(3+) ion was derived for a sample with 12.5% Fe substitution, and gradually decreased to 0.15 eV for the half-Fe-substituted sample. The local octahedral-site distortion of the Fe(3+) ion inside the YMnO3 lattice was similar to that of the Mn(3+) ion, whereas the Jahn-Teller distortion and GdFeO3-type distortion of the Mn(3+) ion were decreased by the spherical high-spin Fe(3+) ions. The combination of the experimental and theoretical data provides both profound insight into the variation of the Jahn-Teller distortion and orbital anisotropy and instructive information about the magnetic structures in these orthorhombic YMn1-xFexO3 thin films.
Collapse
Affiliation(s)
- Shu-Chih Haw
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Jenn-Min Lee
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Shin-Ann Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Kueih-Tzu Lu
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Ming-Tao Lee
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Tun-Wen Pi
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| | - Chih-Hao Lee
- Department of Engineering and System Science, National Tsing Hua University, 30013 Hsinchu, Taiwan
| | - Zhiwei Hu
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany
| | - Jin-Ming Chen
- National Synchrotron Radiation Research Center (NSRRC), 101 Hsin-Ann Road, 30076 Hsinchu, Taiwan.
| |
Collapse
|
21
|
Haverkort MW. Quantyfor core level spectroscopy - excitons, resonances and band excitations in time and frequency domain. ACTA ACUST UNITED AC 2016. [DOI: 10.1088/1742-6596/712/1/012001] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
22
|
Antiferromagnetic proximity effect in epitaxial CoO/NiO/MgO(001) systems. Sci Rep 2016; 6:22355. [PMID: 26932164 PMCID: PMC4773757 DOI: 10.1038/srep22355] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/12/2016] [Indexed: 11/08/2022] Open
Abstract
Magnetic proximity effect between two magnetic layers is an important focus of research for discovering new physical properties of magnetic systems. Antiferromagnets (AFMs) are fundamental systems with magnetic ordering and promising candidate materials in the emerging field of antiferromagnetic spintronics. However, the magnetic proximity effect between antiferromagnetic bilayers is rarely studied because detecting the spin orientation of AFMs is challenging. Using X-ray linear dichroism and magneto-optical Kerr effect measurements, we investigated antiferromagnetic proximity effects in epitaxial CoO/NiO/MgO(001) systems. We found the antiferromagnetic spin of the NiO underwent a spin reorientation transition from in-plane to out-of-plane with increasing NiO thickness, with the existence of vertical exchange spring spin alignment in thick NiO. More interestingly, the Néel temperature of the CoO layer was greatly enhanced by the adjacent NiO layer, with the extent of the enhancement closely dependent on the spin orientation of NiO layer. This phenomenon was attributed to different exchange coupling strengths at the AFM/AFM interface depending on the relative spin directions. Our results indicate a new route for modifying the spin configuration and ordering temperature of AFMs through the magnetic proximity effect near room temperature, which should further benefit the design of AFM spintronic devices.
Collapse
|
23
|
Huang CY, Zhou J, Tra VT, White R, Trappen R, N'Diaye AT, Spencer M, Frye C, Cabrera GB, Nguyen V, LeBeau JM, Chu YH, Holcomb MB. Imaging magnetic and ferroelectric domains and interfacial spins in magnetoelectric La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:504003. [PMID: 26613406 DOI: 10.1088/0953-8984/27/50/504003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Strong magnetoelectric coupling can occur at the interface between ferromagnetic and ferroelectric films. Similar to work on interfacial exchange bias, photoemission electron microscopy was utilized to image both magnetic and ferroelectric domains and the resulting interfacial Ti spin in the same locations of La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures. Multiple image analysis techniques, which could be applicable for a variety of fields needing quantitative data on image switching, confirm both improved magnetic switching and an increased population of interfacial spins with increased thickness of the ultrathin La0.7Sr0.3MnO3 layer. The perpendicular orientation of the interfacial spins is also discussed. This work suggests a magnetoelectric dead layer, with reduced interfacial magnetoelectricity when thin magnetic films are present.
Collapse
Affiliation(s)
- C-Y Huang
- Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Lamirand AD, Soares MM, De Santis M, Ramos AY, Grenier S, Tolentino HCN. Strain driven monoclinic distortion of ultrathin CoO films in the exchange-coupled CoO/FePt/Pt(0 0 1) system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:085001. [PMID: 25604708 DOI: 10.1088/0953-8984/27/8/085001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The structure and strain of ultrathin CoO films grown on a Pt(0 0 1) substrate and on a ferromagnetic FePt pseudomorphic layer on Pt(0 0 1) have been determined with in situ and real time surface x-ray diffraction. The films grow epitaxially on both surfaces with an in-plane hexagonal pattern that yields a pseudo-cubic CoO(1 1 1) surface. A refined x-ray diffraction analysis reveals a slight monoclinic distortion at RT induced by the anisotropic stress at the interface. The tetragonal contribution to the distortion results in a ratio [Formula: see text], opposite to that found in the low temperature bulk CoO phase. This distortion leads to a stable Co(2+) spin configuration within the plane of the film.
Collapse
Affiliation(s)
- Anne D Lamirand
- Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France. CNRS, Institut Néel, F-38042 Grenoble, France
| | | | | | | | | | | |
Collapse
|
25
|
Estrader M, López-Ortega A, Golosovsky IV, Estradé S, Roca AG, Salazar-Alvarez G, López-Conesa L, Tobia D, Winkler E, Ardisson JD, Macedo WAA, Morphis A, Vasilakaki M, Trohidou KN, Gukasov A, Mirebeau I, Makarova OL, Zysler RD, Peiró F, Baró MD, Bergström L, Nogués J. Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe(x)O/Fe3O4 nanoparticles as a case study. NANOSCALE 2015; 7:3002-15. [PMID: 25600147 DOI: 10.1039/c4nr06351a] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.
Collapse
Affiliation(s)
- Marta Estrader
- Departament de Química Inorgànica, Universitat de Barcelona, Diagonal 645, E-08028, Barcelona, Spain.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Li ZA, Fontaíña-Troitiño N, Kovács A, Liébana-Viñas S, Spasova M, Dunin-Borkowski RE, Müller M, Doennig D, Pentcheva R, Farle M, Salgueiriño V. Electrostatic doping as a source for robust ferromagnetism at the interface between antiferromagnetic cobalt oxides. Sci Rep 2015; 5:7997. [PMID: 25613569 PMCID: PMC4303864 DOI: 10.1038/srep07997] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/31/2014] [Indexed: 12/02/2022] Open
Abstract
Polar oxide interfaces are an important focus of research due to their novel functionality which is not available in the bulk constituents. So far, research has focused mainly on heterointerfaces derived from the perovskite structure. It is important to extend our understanding of electronic reconstruction phenomena to a broader class of materials and structure types. Here we report from high-resolution transmission electron microscopy and quantitative magnetometry a robust – above room temperature (Curie temperature TC ≫ 300 K) – environmentally stable- ferromagnetically coupled interface layer between the antiferromagnetic rocksalt CoO core and a 2–4 nm thick antiferromagnetic spinel Co3O4 surface layer in octahedron-shaped nanocrystals. Density functional theory calculations with an on-site Coulomb repulsion parameter identify the origin of the experimentally observed ferromagnetic phase as a charge transfer process (partial reduction) of Co3+ to Co2+ at the CoO/Co3O4 interface, with Co2+ being in the low spin state, unlike the high spin state of its counterpart in CoO. This finding may serve as a guideline for designing new functional nanomagnets based on oxidation resistant antiferromagnetic transition metal oxides.
Collapse
Affiliation(s)
- Zi-An Li
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen 48047, Duisburg (Germany)
| | | | - A Kovács
- Ernst Ruska-Centre and Peter Grünberg Institute, Research Centre Jülich, 52425 Jülich, (Germany)
| | - S Liébana-Viñas
- 1] Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen 48047, Duisburg (Germany) [2] Departamento de Física Aplicada, Universidade de Vigo 36310, Vigo (Spain)
| | - M Spasova
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen 48047, Duisburg (Germany)
| | - R E Dunin-Borkowski
- Ernst Ruska-Centre and Peter Grünberg Institute, Research Centre Jülich, 52425 Jülich, (Germany)
| | - M Müller
- Department of Earth and Environmental Sciences, Section Crystallography, LMU Munich, Theresienstr. 41, 80333 Munich (Germany)
| | - D Doennig
- Department of Earth and Environmental Sciences, Section Crystallography, LMU Munich, Theresienstr. 41, 80333 Munich (Germany)
| | - R Pentcheva
- 1] Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen 48047, Duisburg (Germany) [2] Department of Earth and Environmental Sciences, Section Crystallography, LMU Munich, Theresienstr. 41, 80333 Munich (Germany)
| | - M Farle
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen 48047, Duisburg (Germany)
| | - V Salgueiriño
- Departamento de Física Aplicada, Universidade de Vigo 36310, Vigo (Spain)
| |
Collapse
|
27
|
Oh SH, Shin RH, Lefèvre C, Thomasson A, Roulland F, Shin Y, Kim DH, Kim JY, Demchenko A, Leuvrey C, Mény C, Jo W, Viart N. Incorporation of cobalt ions into magnetoelectric gallium ferrite epitaxial films: tuning of conductivity and magnetization. RSC Adv 2015. [DOI: 10.1039/c5ra03609g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Doping Ga0.6Fe1.4O3 thin films with magnetic Co2+ ions leads to a strong reduction in the charge conduction and does not lead to any modification of the ferrimagnetic transition. This is absolutely comparable to that observed with Mg-doping.
Collapse
|
28
|
Indra A, Menezes PW, Sahraie NR, Bergmann A, Das C, Tallarida M, Schmeißer D, Strasser P, Driess M. Unification of Catalytic Water Oxidation and Oxygen Reduction Reactions: Amorphous Beat Crystalline Cobalt Iron Oxides. J Am Chem Soc 2014; 136:17530-6. [DOI: 10.1021/ja509348t] [Citation(s) in RCA: 486] [Impact Index Per Article: 48.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Arindam Indra
- Metalorganics
and Inorganic Materials, Department of Chemistry, Technische Universität Berlin, Straße des 17 Juni 135, Sekr. C2, 10623 Berlin, Germany
| | - Prashanth W. Menezes
- Metalorganics
and Inorganic Materials, Department of Chemistry, Technische Universität Berlin, Straße des 17 Juni 135, Sekr. C2, 10623 Berlin, Germany
| | - Nastaran Ranjbar Sahraie
- The
Electrochemical Energy, Catalysis, and Materials Science Group, Department
of Chemistry, Technische Universität Berlin, Straße des
17 Juni 124, Sekr. TC3, 10623 Berlin, Germany
| | - Arno Bergmann
- The
Electrochemical Energy, Catalysis, and Materials Science Group, Department
of Chemistry, Technische Universität Berlin, Straße des
17 Juni 124, Sekr. TC3, 10623 Berlin, Germany
| | - Chittaranjan Das
- Applied
Physics and Sensors, Brandenburg University of Technology Cottbus, Konrad Wachsmann Allee 17, 03046 Cottbus, Germany
| | - Massimo Tallarida
- Applied
Physics and Sensors, Brandenburg University of Technology Cottbus, Konrad Wachsmann Allee 17, 03046 Cottbus, Germany
| | - Dieter Schmeißer
- Applied
Physics and Sensors, Brandenburg University of Technology Cottbus, Konrad Wachsmann Allee 17, 03046 Cottbus, Germany
| | - Peter Strasser
- The
Electrochemical Energy, Catalysis, and Materials Science Group, Department
of Chemistry, Technische Universität Berlin, Straße des
17 Juni 124, Sekr. TC3, 10623 Berlin, Germany
- Ertl
Center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology, 500-712 Gwangju, South Korea
| | - Matthias Driess
- Metalorganics
and Inorganic Materials, Department of Chemistry, Technische Universität Berlin, Straße des 17 Juni 135, Sekr. C2, 10623 Berlin, Germany
| |
Collapse
|
29
|
Schrön A, Bechstedt F. Magnetic anisotropy of FeO and CoO: the influence of gradient corrections on exchange and correlation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:486002. [PMID: 24177337 DOI: 10.1088/0953-8984/25/48/486002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We study the formation of local magnetic moments and the magnetic anisotropy of the antiferromagnetic transition-metal compounds FeO and CoO in the framework of the density functional theory. Exchange and correlation are described within two (semi-)local approximations, the local spin-density approximation (LDA) and the generalized gradient approximation (GGA), in order to investigate the role of gradient corrections. An additional on-site Coulomb interaction U is considered in an LDA+U/GGA+U approach and spin-orbit interaction is taken into account. We find that the orbital magnetization is strongly quenched in the GGA+U approach compared to LDA+U results and experimental findings. The quenching is explained in terms of an overestimated exchange enhancement for the partially filled 3d shells due to the gradient corrections inherent in GGA+U.
Collapse
Affiliation(s)
- Andreas Schrön
- Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, D-07743 Jena, Germany. European Theoretical Spectroscopy Facility (ETSF)
| | | |
Collapse
|
30
|
Ge C, Wan X, Pellegrin E, Hu Z, Manuel Valvidares S, Barla A, Liang WI, Chu YH, Zou W, Du Y. Direct observation of rotatable uncompensated spins in the exchange bias system Co/CoO-MgO. NANOSCALE 2013; 5:10236-10241. [PMID: 24056958 DOI: 10.1039/c3nr02013d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have observed a large exchange bias field HE ≈ 2460 Oe and a large coercive field HC ≈ 6200 Oe at T = 2 K for Co/CoO core-shell nanoparticles (~4 nm diameter Co metal core and CoO shell with ~1 nm thickness) embedded in a non-magnetic MgO matrix. Our results are in sharp contrast to the small exchange bias and coercive field in the case of a non-magnetic Al2O3 or C matrix materials reported in previous studies. Using soft X-ray magnetic circular dichroism at the Co-L2,3 edge, we have observed a ferromagnetic signal originating from the antiferromagnetic CoO shell. This gives direct evidence for the existence of rotatable interfacial uncompensated Co spins in the nominally antiferromagnetic CoO shell, thus supporting the uncompensated spin model as a microscopic description of the exchange bias mechanism.
Collapse
Affiliation(s)
- Chuannan Ge
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Frano A, Schierle E, Haverkort MW, Lu Y, Wu M, Blanco-Canosa S, Nwankwo U, Boris AV, Wochner P, Cristiani G, Habermeier HU, Logvenov G, Hinkov V, Benckiser E, Weschke E, Keimer B. Orbital control of noncollinear magnetic order in nickel oxide heterostructures. PHYSICAL REVIEW LETTERS 2013; 111:106804. [PMID: 25166693 DOI: 10.1103/physrevlett.111.106804] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 07/10/2013] [Indexed: 06/03/2023]
Abstract
We have used resonant x-ray diffraction to develop a detailed description of antiferromagnetic ordering in epitaxial superlattices based on two-unit-cell thick layers of the strongly correlated metal LaNiO3. We also report reference experiments on thin films of PrNiO3 and NdNiO3. The resulting data indicate a spiral state whose polarization plane can be controlled by adjusting the Ni d-orbital occupation via two independent mechanisms: epitaxial strain and spatial confinement of the valence electrons. The data are discussed in light of recent theoretical predictions.
Collapse
Affiliation(s)
- A Frano
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany and Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - E Schierle
- Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - M W Haverkort
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Y Lu
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - M Wu
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - S Blanco-Canosa
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - U Nwankwo
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - A V Boris
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - P Wochner
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - G Cristiani
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - H U Habermeier
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - G Logvenov
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - V Hinkov
- Quantum Matter Institute, University of British Columbia, Vancouver, British Colombia V6T 1Z1, Canada
| | - E Benckiser
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - E Weschke
- Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - B Keimer
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| |
Collapse
|
32
|
Heinz K, Hammer L. Epitaxial cobalt oxide films on Ir(100)-the importance of crystallographic analyses. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:173001. [PMID: 23535176 DOI: 10.1088/0953-8984/25/17/173001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Epitaxial cobalt oxide films on Ir(100) exhibit a rich scenario of different structural phases which are reviewed in this paper. The great majority of phases could be, as a rare case, crystallographically described by the joint application of atomically resolved STM and quantitative LEED, whereby structural surprises were more the rule than the exception. So, the oxide grows in the polar (111) orientation for both the Co3O4 and CoO stoichiometry on the bare Ir substrate in spite of the latter's square symmetry. Moreover, the film orientation can be tuned to non-polar (100) growth when one or several pseudomorphic Co layers are introduced as an interface between oxide and Ir substrate. By using the nanostructured Ir(100)-(5 × 1)-H phase as a template a nanostructured Co film can be formed whose oxidation leads to a nanostructured oxide. The nominally polar films circumvent the polarity problem by appropriate surface terminations. That of CoO(111) is, again as a surprise, realized by a switch from rocksalt-type to wurtzite-type stacking near the surface, by which the latter becomes metallic. The stepwise oxidation of a pseudomorphic Co layer on the bare Ir substrate leads to the sequential formation of rocksalt-type tetrahedral Co-O building blocks (with intermediate BN-type blocks) whereby the Co species more and more assume positions determined by the inner-oxidic binding.
Collapse
Affiliation(s)
- K Heinz
- Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen, Germany.
| | | |
Collapse
|
33
|
Yang JC, He Q, Suresha SJ, Kuo CY, Peng CY, Haislmaier RC, Motyka MA, Sheng G, Adamo C, Lin HJ, Hu Z, Chang L, Tjeng LH, Arenholz E, Podraza NJ, Bernhagen M, Uecker R, Schlom DG, Gopalan V, Chen LQ, Chen CT, Ramesh R, Chu YH. Orthorhombic BiFeO3. PHYSICAL REVIEW LETTERS 2012; 109:247606. [PMID: 23368382 DOI: 10.1103/physrevlett.109.247606] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 09/07/2012] [Indexed: 05/12/2023]
Abstract
A new orthorhombic phase of the multiferroic BiFeO3 has been created via strain engineering by growing it on a NdScO(3)(110)(o) substrate. The tensile-strained orthorhombic BiFeO3 phase is ferroelectric and antiferromagnetic at room temperature. A combination of nonlinear optical second harmonic generation and piezoresponse force microscopy revealed that the ferroelectric polarization in the orthorhombic phase is along the in-plane {110}(pc) directions. In addition, the corresponding rotation of the antiferromagnetic axis in this new phase was observed using x-ray linear dichroism.
Collapse
Affiliation(s)
- J C Yang
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Surnev S, Fortunelli A, Netzer FP. Structure-property relationship and chemical aspects of oxide-metal hybrid nanostructures. Chem Rev 2012; 113:4314-72. [PMID: 23237602 DOI: 10.1021/cr300307n] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Svetlozar Surnev
- Surface and Interface Physics, Institute of Physics, Karl-Franzens University, Graz A-8010 Graz, Austria
| | | | | |
Collapse
|
35
|
Lodi Rizzini A, Krull C, Balashov T, Mugarza A, Nistor C, Yakhou F, Sessi V, Klyatskaya S, Ruben M, Stepanow S, Gambardella P. Exchange biasing single molecule magnets: coupling of TbPc2 to antiferromagnetic layers. NANO LETTERS 2012; 12:5703-7. [PMID: 23046484 DOI: 10.1021/nl302918d] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We investigate the possibility to induce exchange bias between single molecule magnets (SMM) and metallic or oxide antiferromagnetic substrates. Element-resolved X-ray magnetic circular dichroism measurements reveal, respectively, the presence and absence of unidirectional exchange anisotropy for TbPc(2) SMM deposited on antiferromagnetic Mn and CoO layers. TbPc(2) deposited on Mn thin films present magnetic hysteresis and a negative horizontal shift of the Tb magnetization loop after field cooling, consistent with the observation of pinned spins in the Mn layer coupled parallel to the Tb magnetic moment. Conversely, molecules deposited on CoO substrates present paramagnetic magnetization loops with no indication of exchange bias. These experiments demonstrate the ability of SMM to polarize the pinned uncompensated spins of an antiferromagnet during field-cooling and realize metal-organic exchange-biased heterostructures using antiferromagnetic pinning layers.
Collapse
Affiliation(s)
- A Lodi Rizzini
- Catalan Institute of Nanotechnology (ICN), UAB Campus, E-08193 Barcelona, Spain
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Liao K, Fiorin V, Jenkins SJ, King DA. Microcalorimetry of oxygen adsorption on fcc Co{110}. Phys Chem Chem Phys 2012; 14:7528-32. [PMID: 22531709 DOI: 10.1039/c2cp40549k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage. The initial heat of adsorption of 633 kJ mol(-1) is similar to heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron. As the coverage increases, the heat of adsorption and sticking probability drop very rapidly up to the onset of oxidation. As already observed for other oxygen-metal surface systems, strong lateral adatom repulsions are responsible for the transition from the chemisorption regime to oxide film formation at higher coverage. The heat of oxide formation at the onset is 475 kJ mol(-1), which is consistent with the formation of CoO crystallites. The oxide film formation is discussed in terms of nucleation and island growth, and the Mott-Cabrera mechanisms, the latter being evidenced by the relatively constant heat of adsorption and sticking probability in contrast to the nickel and iron oxidation cases.
Collapse
Affiliation(s)
- Kristine Liao
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | | | | | | |
Collapse
|
37
|
Ilyasov VV, Velikokhatskii DA, Ershov IV, Nikiforov IY, Zhdanova TP. Ab initio calculations of chemical bond parameters and the band structure of a two-dimensional system: Graphene/MnO(001). J STRUCT CHEM+ 2011. [DOI: 10.1134/s0022476611050027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
38
|
Zhang JX, He Q, Trassin M, Luo W, Yi D, Rossell MD, Yu P, You L, Wang CH, Kuo CY, Heron JT, Hu Z, Zeches RJ, Lin HJ, Tanaka A, Chen CT, Tjeng LH, Chu YH, Ramesh R. Microscopic origin of the giant ferroelectric polarization in tetragonal-like BiFeO(3). PHYSICAL REVIEW LETTERS 2011; 107:147602. [PMID: 22107234 DOI: 10.1103/physrevlett.107.147602] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2011] [Indexed: 05/12/2023]
Abstract
We report direct experimental evidence for a room-temperature, ∼130 μC/cm(2) ferroelectric polarization from the tetragonal-like BiFeO(3) phase. The physical origin of this remarkable enhancement of ferroelectric polarization has been investigated by a combination of x-ray absorption spectroscopy, scanning transmission electron microscopy, and first principles calculations. A large strain-induced Fe-ion displacement relative to the oxygen octahedra, combined with the contribution of Bi 6s lone pair electrons, is the mechanism driving the large ferroelectric polarization in this tetragonal-like phase.
Collapse
Affiliation(s)
- J X Zhang
- Department of Physics, University of California, Berkeley, California 94720, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
Papaefthimiou V, Dintzer T, Dupuis V, Tamion A, Tournus F, Hillion A, Teschner D, Hävecker M, Knop-Gericke A, Schlögl R, Zafeiratos S. Nontrivial redox behavior of nanosized cobalt: new insights from ambient pressure X-ray photoelectron and absorption spectroscopies. ACS NANO 2011; 5:2182-2190. [PMID: 21309559 DOI: 10.1021/nn103392x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The reduction and oxidation of carbon-supported cobalt nanoparticles (3.50±0.22 nm) and a Co (0001) single crystal was investigated by ambient pressure X-ray photoelectron (APPES) and X-ray absorption (XAS) spectroscopies, applied in situ under 0.2 mbar hydrogen or oxygen atmospheres and at temperatures up to 620 K. It was found that cobalt nanoparticles are readily oxidized to a distinct CoO phase, which is significantly more stable to further oxidation or reduction compared to the thick oxide films formed on the Co(0001) crystal. The nontrivial size-dependence of redox behavior is followed by a difference in the electronic structure as suggested by theoretical simulations of the Co L-edge absorption spectra. In particular, contrary to the stable rocksalt and spinel phases that exist in the bulk oxides, cobalt nanoparticles contain a significant portion of metastable wurtzite-type CoO.
Collapse
Affiliation(s)
- Vasiliki Papaefthimiou
- Laboratoire LMSPC UMR7515, CNRS, University of Strasbourg, F-67087, Strasbourg cedex 2, France
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Miguel J, Abrudan R, Bernien M, Piantek M, Tieg C, Kirschner J, Kuch W. Magnetic domain coupling study in single-crystalline Fe/CoO bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:185004. [PMID: 21825450 DOI: 10.1088/0953-8984/21/18/185004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report on a study of the magnetic domain coupling in epitaxial wedge-shaped Fe layers deposited onto CoO/Ag(001). By using photoelectron emission microscopy (PEEM) in combination with x-ray magnetic circular and linear dichroism (XMCD, XMLD), we imaged the ferromagnetic and antiferromagnetic domains present in the Fe and CoO layers, respectively, below the CoO magnetic ordering temperature. The uncompensated Co spins at the Fe/CoO interface were revealed by XMCD-PEEM and were found to be coupled parallel to the magnetization of the Fe layer. An increase of the CoO XMLD contrast is visible for Fe thicknesses below 2 ML, where the Fe layer lacks magnetic long-range order.
Collapse
Affiliation(s)
- J Miguel
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | | | | | | | | | | | | |
Collapse
|
41
|
Chang CF, Hu Z, Wu H, Burnus T, Hollmann N, Benomar M, Lorenz T, Tanaka A, Lin HJ, Hsieh HH, Chen CT, Tjeng LH. Spin blockade, orbital occupation, and charge ordering in La1.5Sr0.5CoO4. PHYSICAL REVIEW LETTERS 2009; 102:116401. [PMID: 19392219 DOI: 10.1103/physrevlett.102.116401] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Indexed: 05/27/2023]
Abstract
Using Co-L2,3 and O-K x-ray absorption spectroscopy, we reveal that the charge ordering in La1.5Sr0.5CoO4 involves high spin (S=3/2) Co2+ and low spin (S=0) Co3+ ions. This provides evidence for the spin-blockade phenomenon as a source for the extremely insulating nature of the La2-xSrxCoO4 series. The associated e{g}{2} and e{g}{0} orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the nonmagnetic (S=0) Co3+ ions. From the identification of the bands we infer that La1.5Sr0.5CoO4 is a narrow band material.
Collapse
Affiliation(s)
- C F Chang
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
42
|
Haverkort MW, Hu Z, Cezar JC, Burnus T, Hartmann H, Reuther M, Zobel C, Lorenz T, Tanaka A, Brookes NB, Hsieh HH, Lin HJ, Chen CT, Tjeng LH. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism. PHYSICAL REVIEW LETTERS 2006; 97:176405. [PMID: 17155490 DOI: 10.1103/physrevlett.97.176405] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Indexed: 05/12/2023]
Abstract
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.
Collapse
Affiliation(s)
- M W Haverkort
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Finazzi M, Brambilla A, Biagioni P, Graf J, Gweon GH, Scholl A, Lanzara A, Duò L. Interface coupling transition in a thin epitaxial antiferromagnetic film interacting with a ferromagnetic substrate. PHYSICAL REVIEW LETTERS 2006; 97:097202. [PMID: 17026395 DOI: 10.1103/physrevlett.97.097202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Indexed: 05/12/2023]
Abstract
We report experimental evidence for a transition in the interface coupling between an antiferromagnetic film and a ferromagnetic substrate. The transition is observed in a thin epitaxial NiO film grown on top of Fe(001) as the film thickness is increased. Photoemission electron microscopy excited with linearly polarized x rays shows that the NiO film is antiferromagnetic at room temperature with in-plane uniaxial magnetic anisotropy. The anisotropy axis is perpendicular to the Fe substrate magnetization when the NiO thickness is less than about 15 A, but rapidly becomes parallel to the Fe magnetization for a NiO coverage higher than 25 A.
Collapse
Affiliation(s)
- M Finazzi
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
| | | | | | | | | | | | | | | |
Collapse
|