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Mydeen K, Jesche A, Meier-Kirchner K, Schwarz U, Geibel C, Rosner H, Nicklas M. Electron Doping of the Iron-Arsenide Superconductor CeFeAsO Controlled by Hydrostatic Pressure. PHYSICAL REVIEW LETTERS 2020; 125:207001. [PMID: 33258641 DOI: 10.1103/physrevlett.125.207001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 09/25/2020] [Accepted: 10/14/2020] [Indexed: 06/12/2023]
Abstract
In the iron-pnictide material CeFeAsO not only the Fe moments, but also the local 4f moments of the Ce order antiferromagnetically at low temperatures. We elucidate on the peculiar role of the Ce on the emergence of superconductivity. While application of pressure suppresses the iron SDW ordering temperature monotonously up to 4 GPa, the Ce-4f magnetism is stabilized until both types of magnetic orders disappear abruptly and a narrow SC dome develops. With further increasing pressure characteristics of a Kondo-lattice system become more and more apparent in the electrical resistivity. This suggests a connection of the emergence of superconductivity with the extinction of the magnetic order and the onset of Kondo screening of the Ce-4f moments.
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Affiliation(s)
- K Mydeen
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
| | - A Jesche
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - K Meier-Kirchner
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
| | - U Schwarz
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
| | - C Geibel
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
| | - H Rosner
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
| | - M Nicklas
- Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden
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2
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Ghising P, Das D, Das S, Hossain Z. Kondo effect with tunable spin-orbit interaction in LaTiO 3/CeTiO 3/SrTiO 3 heterostructure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:285002. [PMID: 29855435 DOI: 10.1088/1361-648x/aac977] [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 have fabricated epitaxial films of CeTiO3 (CTO) on (0 0 1) oriented SrTiO3 (STO) substrates, which exhibit highly insulating and diamagnetic properties. X-ray photoelectron spectroscopy was used to establish the 3+ valence state of the Ce and Ti ions. Furthermore, we have also fabricated δ (CTO) doped LaTiO3 (LTO)/SrTiO3 thin films which exhibit variety of interesting properties including Kondo effect and spin-orbit interaction (SOI) at low temperatures. The SOI shows a non-monotonic behaviour as the thickness of the CTO layer is increased and is reflected in the value of characteristic SOI field ([Formula: see text]) obtained from weak anti-localization fitting. The maximum value of [Formula: see text] is 1.00 T for δ layer thickness of 6 u.c. This non-monotonic behaviour of SOI is attributed to the strong screening of the confining potential at the interface. The screening effect is enhanced by the CTO layer thickness and the dielectric constant of STO which increases at low temperatures. Due to the strong screening, electrons confined at the interface are spread deeper into the STO bulk where it starts to populate the Ti [Formula: see text] subbands; consequently the Fermi level crosses over from [Formula: see text] to the [Formula: see text] subbands. At the crossover region of [Formula: see text] where there is orbital mixing, SOI goes through a maximum.
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Affiliation(s)
- Pramod Ghising
- Department of Physics, Condensed Matter-Low Dimensional Systems Laboratory, Indian Institute of Technology, Kanpur-208016, India
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3
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Theory of Electron Spin Resonance in Ferromagnetically Correlated Heavy Fermion Compounds. MAGNETOCHEMISTRY 2018. [DOI: 10.3390/magnetochemistry4020027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Nadeem K, Zhang W, Chen DY, Ren ZA, Qiu XG. Slow Spin Dynamics in Superconducting Ca0.9Ce0.1Fe2As2. Sci Rep 2015; 5:10700. [PMID: 26024047 PMCID: PMC4448653 DOI: 10.1038/srep10700] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/27/2015] [Indexed: 11/13/2022] Open
Abstract
Slow spin dynamics has been observed in superconducting under-doped Ca0.9Ce0.1Fe2As2 single crystal. Below 100 K, the system exhibits hysteresis in the cooling and warming protocols of temperature dependent resistivity due to first order tetragonal to orthorhombic structural transition with simultaneous magnetic transition from paramagnetic to spin density wave antiferromagnetic state of the iron (Fe) ions. Zero field cooled/field cooled (ZFC/FC) magnetization curves showed splitting at 32 K followed by a sharp increase of the FC curve and then FC plateau at low temperatures. Slow spin relaxation in both the ZFC and FC protocols was observed which is typical for spin-glass system. The system also showed features analogue to spin-glass behavior such as ZFC peak, FC plateau, ZFC slow spin relaxation, magnetic hysteresis, and ZFC ac memory effect. The spin-glass like behavior was rather weak and vanished at higher fields. The origin of the slow spin dynamics could be the inhomogeneous distribution of the cerium (Ce) spins ordered along the c-axis OR interactions between Fe and Ce spins which lead to magnetic frustration of Ce spins. All these findings support the coexistence of slow spin dynamics of Ce spins and superconductivity in Ca0.9Ce0.1Fe2As2 single crystal.
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Affiliation(s)
- K. Nadeem
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
- Department of Physics, International Islamic University, H-10, Islamabad 44000, Pakistan
| | - W. Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
- School of Physical Science and Technology & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China
| | - D. Y. Chen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
| | - Z. A. Ren
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
| | - X. G. Qiu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
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Khuntia P, Peratheepan P, Strydom AM, Utsumi Y, Ko KT, Tsuei KD, Tjeng LH, Steglich F, Baenitz M. Contiguous 3d and 4f magnetism: strongly correlated 3d electrons in YbFe2Al10. PHYSICAL REVIEW LETTERS 2014; 113:216403. [PMID: 25479509 DOI: 10.1103/physrevlett.113.216403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Indexed: 06/04/2023]
Abstract
We present magnetization, specific heat, and (27)Al NMR investigations on YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a ln(T0/T) divergence of the low-T specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard-x-ray photoemission spectroscopy study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, Yb(3+) carries a full and stable moment, and Fe carries a moment of about 3.1 μB. The enhanced value of the Sommerfeld-Wilson ratio and the dynamic scaling of the spin-lattice relaxation rate divided by T[(27)(1/T1T)] with static susceptibility suggests admixed ferromagnetic correlations. (27)(1/T1T) simultaneously tracks the valence fluctuations from the 4f Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe 3d moments at low temperature; the latter evolve out of an Yb 4f admixed conduction band.
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Affiliation(s)
- P Khuntia
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - P Peratheepan
- Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa and Department of Physics, Eastern University, Vantharumoolai, Chenkalady 30350, Sri Lanka
| | - A M Strydom
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany and Highly Correlated Matter Research Group, Physics Department, University of Johannesburg, P.O. Box 524, Auckland Park 2006, South Africa
| | - Y Utsumi
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - K-T Ko
- Max Planck POSTECH Center for Complex Phase Materials, 01187 Dresden, Germany and Pohang 790-784, Korea
| | - K-D Tsuei
- National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30077, Taiwan
| | - L H Tjeng
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - F Steglich
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - M Baenitz
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
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6
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Luo Y, Pourovskii L, Rowley SE, Li Y, Feng C, Georges A, Dai J, Cao G, Xu Z, Si Q, Ong NP. Heavy-fermion quantum criticality and destruction of the Kondo effect in a nickel oxypnictide. NATURE MATERIALS 2014; 13:777-781. [PMID: 24859644 DOI: 10.1038/nmat3991] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 04/24/2014] [Indexed: 06/03/2023]
Abstract
A quantum critical point arises at a continuous transformation between distinct phases of matter at zero temperature. Studies in antiferromagnetic heavy-fermion materials have revealed that quantum criticality has several classes, with an unconventional type that involves a critical destruction of the Kondo entanglement. To understand such varieties, it is important to extend the materials basis beyond the usual setting of intermetallic compounds. Here we show that a nickel oxypnictide, CeNiAsO, exhibits a heavy-fermion antiferromagnetic quantum critical point as a function of either pressure or P/As substitution. At the quantum critical point, non-Fermi-liquid behaviour appears, which is accompanied by a divergent effective carrier mass. Across the quantum critical point, the low-temperature Hall coefficient undergoes a rapid sign change, suggesting a sudden jump of the Fermi surface and a destruction of the Kondo effect. Our results imply that the enormous materials basis for the oxypnictides, which has been so crucial in the search for high-temperature superconductivity, will also play a vital role in the effort to establish the universality classes of quantum criticality in strongly correlated electron systems.
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Affiliation(s)
- Yongkang Luo
- 1] Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China [2] Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Leonid Pourovskii
- 1] Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau Cedex, France [2] Swedish e-science Research Centre (SeRC), Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping 58183, Sweden
| | - S E Rowley
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - Yuke Li
- Department of Physics, Hangzhou Normal University, Hangzhou 310036, China
| | - Chunmu Feng
- Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
| | - Antoine Georges
- Centre de Physique Théorique, École Polytechnique, CNRS, 91128 Palaiseau Cedex, France
| | - Jianhui Dai
- Department of Physics, Hangzhou Normal University, Hangzhou 310036, China
| | - Guanghan Cao
- Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
| | - Zhu'an Xu
- Department of Physics and State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China
| | - Qimiao Si
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - N P Ong
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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7
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Ren YZ, Tong NH, Xie XC. Cluster mean-field theory study of J1-J2 Heisenberg model on a square lattice. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:115601. [PMID: 24589877 DOI: 10.1088/0953-8984/26/11/115601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study the spin-1/2 J1-J2 Heisenberg model on a square lattice using the cluster mean-field theory. We find a rapid convergence of phase boundaries with increasing cluster size. By extrapolating the cluster size L to infinity, we obtain accurate phase boundaries J(c1)(2) ≈ 0.42 (between the Néel antiferromagnetic phase and non-magnetic phase), and J(c2)(2) ≈ 0.59 (between non-magnetic phase and the collinear antiferromagnetic phase). Our results support the second-order phase transition at J(c1)(2) and the first-order one at J(c2)(2). For the spin-anisotropic J1-J2 model, we present its finite temperature phase diagram and demonstrate that the non-magnetic state is unstable towards the first-order phase transition under intermediate spin anisotropy.
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Affiliation(s)
- Yong-Zhi Ren
- Department of Physics, Renmin University of China, 100872 Beijing, People's Republic of China
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8
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Zhao J, Liu H, Ehm L, Dong D, Chen Z, Liu Q, Hu W, Wang N, Jin C. Pressure-Induced Phase Transitions and Correlation between Structure and Superconductivity in Iron-Based Superconductor Ce(O0.84F0.16)FeAs. Inorg Chem 2013; 52:8067-73. [DOI: 10.1021/ic400727g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jinggeng Zhao
- Natural Science Research Center, Academy of Fundamental and Interdisciplinary
Sciences, Harbin Institute of Technology, Harbin 150080, China
- Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Haozhe Liu
- Natural Science Research Center, Academy of Fundamental and Interdisciplinary
Sciences, Harbin Institute of Technology, Harbin 150080, China
| | - Lars Ehm
- Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, United States
- Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794, United States
| | - Dawei Dong
- Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973, United States
- Department of Physics, Harbin Institute of Technology, Harbin 150080, China
| | - Zhiqiang Chen
- Mineral Physics Institute, Stony Brook University, Stony Brook, New York 11794, United States
| | - Qingqing Liu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wanzheng Hu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Nanlin Wang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Changqing Jin
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Chen JM, Haw SC, Lee JM, Chen SA, Lu KT, Deng MJ, Chen SW, Ishii H, Hiraoka N, Tsuei KD. Electronic structure and characteristics of Fe 3d valence states of Fe(1.01)Se superconductors under pressure probed by x-ray absorption spectroscopy and resonant x-ray emission spectroscopy. J Chem Phys 2012; 137:244702. [PMID: 23277947 DOI: 10.1063/1.4772466] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The electronic structure and characteristics of Fe 3d valence states of iron-chalcogenide Fe(1.01)Se superconductors under pressure were probed with x-ray absorption spectroscopy and resonant x-ray emission spectroscopy (RXES). The intensity of the pre-edge peak at ~7112.7 eV of the Fe K-edge x-ray absorption spectrum of Fe(1.01)Se decreases for pressure from 0.5 GPa increased to 6.9 GPa. The satellite line Kβ' was reduced in intensity upon applying pressure and became absent for pressure 52 GPa. Fe(1.01)Se shows a small net magnetic moment of Fe(2+), likely arising from strong Fe-Fe spin fluctuations. The 1s3p-RXES spectra of Fe(1.01)Se at pressures 0.5, 6.9, and 52 GPa recorded at the Fe K-edge reveal that unoccupied Fe 3d states exhibit a delocalized character, stemming from hybridization of Fe 3d and 4p orbitals arising from a local distortion around the Fe atom in a tetrahedral site. Application of pressure causes suppression of this on-site Fe 3d-Fe 4p hybridization, and thereby decreases the intensity of the pre-edge feature in the Fe K-edge absorption spectrum of Fe(1.01)Se. Compression enhances spin fluctuations at Fe sites in Fe(1.01)Se and increases the corresponding T(c), through a competition between nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic superexchange interactions. This result aids our understanding of the physics underlying iron-based superconductors.
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Affiliation(s)
- J M Chen
- National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
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Kitagawa S, Ishida K, Nakamura T, Matoba M, Kamihara Y. Ferromagnetic quantum critical point in heavy-fermion iron oxypnictide Ce(Ru(1-x)Fe(x))PO. PHYSICAL REVIEW LETTERS 2012; 109:227004. [PMID: 23368152 DOI: 10.1103/physrevlett.109.227004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Indexed: 06/01/2023]
Abstract
We have performed (31)P-NMR measurements on Ce(Ru(1-x)Fe(x))PO in order to investigate ferromagnetic (FM) quantum criticality, since a heavy-fermion (HF) ferromagnet CeRuPO with a two-dimensional structure turns into a HF paramagnet by an isovalent Fe substitution for Ru. We found that Ce(Ru(0.15)Fe(0.85))PO shows critical fluctuations down to ~0.3 K, as well as the continuous suppression of Curie temperature and the ordered moments by the Fe substitution. These experimental results suggest the presence of a FM quantum critical point (QCP) at x~0.86, which is a rare example among itinerant ferromagnets. In addition, we point out that the critical behaviors in Ce(Ru(0.15)Fe(0.85))PO share a similarity with those in YbRh(2)Si(2), where the local criticality of f electrons has been discussed. We reveal that Ce(Ru(1-x)Fe(x))PO is a new system to study FM quantum criticality in HF compounds.
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Affiliation(s)
- S Kitagawa
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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Lausberg S, Spehling J, Steppke A, Jesche A, Luetkens H, Amato A, Baines C, Krellner C, Brando M, Geibel C, Klauss HH, Steglich F. Avoided ferromagnetic quantum critical point: unusual short-range ordered state in CeFePO. PHYSICAL REVIEW LETTERS 2012; 109:216402. [PMID: 23215601 DOI: 10.1103/physrevlett.109.216402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Indexed: 06/01/2023]
Abstract
Cerium 4f electronic spin dynamics in single crystals of the heavy-fermion system CeFePO is studied by means of ac susceptibility, specific heat, and muon-spin relaxation (μSR). Short-range static magnetism occurs below the freezing temperature T(g) ≈ 0.7 K, which prevents the system from accessing a putative ferromagnetic quantum critical point. In the μSR, the sample-averaged muon asymmetry function is dominated by strongly inhomogeneous spin fluctuations below 10 K and exhibits a characteristic time-field scaling relation expected from glassy spin dynamics, strongly evidencing cooperative and critical spin fluctuations. The overall behavior can be ascribed neither to canonical spin glasses nor other disorder-driven mechanisms.
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Affiliation(s)
- S Lausberg
- Max-Planck-Institute for Chemical Physics of Solids, D-01187 Dresden, Germany.
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Sarkar R, Baenitz M, Jesche A, Geibel C, Steglich F. Interplay between Fe 3d and Ce 4f magnetism and Kondo interaction in CeFeAs(1-x)P(x)O probed by 75As and 31P NMR. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:135602. [PMID: 22407024 DOI: 10.1088/0953-8984/24/13/135602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A detailed (31)P (I = 1/2) and (75)As (I = 3/2) NMR study on polycrystalline CeFeAs(1-x)P(x)O alloys is presented. The magnetism of CeFeAsO changes drastically upon P substitution on the As site. CeFePO is a heavy fermion system without long-range order whereas CeFeAsO exhibits an Fe 3d SDW type of ordering accompanied by a structural transition from tetragonal (TT) to orthorhombic (OT) structure. Furthermore, Ce 4f(1) orders antiferromagnetically (AFM) at low temperature. At the critical concentration where the Fe magnetism is diminished the Ce-Ce interaction changes to a ferromagnetic (FM) type of ordering. Three representative samples of the CeFeAs(1-x)P(x)O (x = 0.05, 0.3 and 0.9) series are systematically investigated. (1) For the x = 0.05 alloy a drastic change of the linewidth at 130 K indicates the AFM-SDW type of ordering of Fe and the structural change from the TT to the OT phase. The linewidth roughly measures the internal field in the ordered state and the transition is most likely first order. The small and nearly constant shift from (31)P and (75)As NMR suggests the presence of competing hyperfine interactions between the nuclear spins and the 4f and 3d ions of Ce and Fe. (2) For the x = 0.3 alloy, the evolution of the Fe-SDW type of order takes place at around 70 K corroborating the results of bulk measurement and μSR. Here we found evidence for phase separation of paramagnetic and magnetic SDW phases. (3) In contrast to the heavy fermion CeFePO for the x = 0.9 alloy a phase transition is found at 2 K. The field-dependent NMR shift gives evidence of FM ordering. Above the ordering the spin-lattice relaxation rate (31)(1/T(1)) shows unconventional, non-Korringa-like behaviour which indicates a complex interplay of Kondo and FM fluctuations.
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Affiliation(s)
- R Sarkar
- Max-Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany.
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Kitagawa S, Ikeda H, Nakai Y, Hattori T, Ishida K, Kamihara Y, Hirano M, Hosono H. Metamagnetic behavior and Kondo breakdown in heavy-fermion CeFePO. PHYSICAL REVIEW LETTERS 2011; 107:277002. [PMID: 22243324 DOI: 10.1103/physrevlett.107.277002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Indexed: 05/31/2023]
Abstract
We report that nonmagnetic heavy-fermion (HF) iron oxypnictide CeFePO with two-dimensional XY-type anisotropy shows a metamagnetic behavior at the metamagnetic field H(M)≃4 T perpendicular to the c axis and that a critical behavior is observed around H(M). Although the magnetic character is entirely different from that in other Ce-based HF metamagnets, H(M) in these metamagnets is linearly proportional to the inverse of the effective mass, or to the temperature where the susceptibility shows a peak. This finding suggests that H(M) is a magnetic field breaking the local Kondo singlet, and the critical behavior around H(M) is driven by the Kondo breakdown accompanied by the Fermi-surface instability.
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Affiliation(s)
- S Kitagawa
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto, Japan.
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Abrahams E, Si Q. Quantum criticality in the iron pnictides and chalcogenides. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:223201. [PMID: 21593557 DOI: 10.1088/0953-8984/23/22/223201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Superconductivity in the iron pnictides and chalcogenides arises at the border of antiferromagnetism, which raises the question of the role of quantum criticality. In this topical review, we describe the theoretical work that led to the prediction of a magnetic quantum critical point arising out of a competition between electronic localization and itinerancy, and the proposal for accessing it by using isoelectronic P substitution for As in the undoped iron pnictides. We go on to compile the emerging experimental evidence in support of the existence of such a quantum critical point in isoelectronically tuned iron pnictides. We close by discussing the implications of these results for the physics of the iron pnictides and chalcogenides.
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Affiliation(s)
- Elihu Abrahams
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA.
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Luo Y, Han H, Tan H, Lin X, Li Y, Jiang S, Feng C, Dai J, Cao G, Xu Z, Li S. CeNiAsO: an antiferromagnetic dense Kondo lattice. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:175701. [PMID: 21474880 DOI: 10.1088/0953-8984/23/17/175701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A cerium-containing pnictide, CeNiAsO, crystallized in the ZrCuSiAs-type structure, has been investigated by measuring transport and magnetic properties, as well as specific heat. We found that CeNiAsO is an antiferromagnetic dense Kondo lattice metallic compound with Kondo scale T(K) ∼15 K and shows an enhanced Sommerfeld coefficient of γ(0) ∼203 mJ mol K(-2). While no superconductivity can be observed down to 30 mK, Ce ions exhibit two successive antiferromagnetic (AFM) transitions. We propose that the magnetic moment of the Ce ion could align in the G-type AFM order below the first transition at T(N1)=9.3 K, and it might be modified into the C-type AFM order below a lower transition at T(N2)=7.3 K. Our results indicate that the 3d-4f interlayer Kondo interactions play an important role in Ni-based Ce-containing pnictides.
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Affiliation(s)
- Yongkang Luo
- Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China
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Janoschek M, Baumbach RE, Hamlin JJ, Lum IK, Maple MB. The non-centrosymmetric heavy fermion ferromagnet Sm₂Fe₁₂P₇. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:094221. [PMID: 21339574 DOI: 10.1088/0953-8984/23/9/094221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report measurements of the electrical resistivity, magnetization and specific heat on single crystals of the non-centrosymmetric compound Sm2Fe12P7. The magnetization measurements demonstrate that Sm2Fe12P7 exhibits ferromagnetic order below TM, 1 = 6.3 K. The ratio of the effective magnetic moment obtained from a Curie-Weiss fit to the magnetic susceptibility in the paramagnetic state, to the saturation magnetic moment in the ordered state indicates that the ordered state is associated with itinerant electrons. The specific heat measurements reveal an enhanced value for the coefficient of the electronic specific heat γ ∼ 450 mJ mol (-1) K (-2) that is accompanied by a large coefficient A of the T(2) term in the electrical resistivity at low temperatures, suggesting a heavy fermion ground state. Several consecutive magnetic phase transitions indicative of competing magnetic energy scales and the observation of a metamagnetic transition in the magnetization data additionally suggest proximity to a quantum critical point.
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Affiliation(s)
- M Janoschek
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
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19
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Holder MG, Jesche A, Lombardo P, Hayn R, Vyalikh DV, Danzenbächer S, Kummer K, Krellner C, Geibel C, Kucherenko Y, Kim TK, Follath R, Molodtsov SL, Laubschat C. CeFePO: f-d hybridization and quenching of superconductivity. PHYSICAL REVIEW LETTERS 2010; 104:096402. [PMID: 20366999 DOI: 10.1103/physrevlett.104.096402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Indexed: 05/29/2023]
Abstract
As a homologue to the new, Fe-based type of high-temperature superconductors, the electronic structure of the heavy-fermion compound CeFePO was studied by means of angle-resolved resonant photoemission. It was experimentally found-and later on confirmed by local-density approximation (LDA) as well as dynamical mean-field theory (DMFT) calculations-that the Ce 4f states hybridize to the Fe 3d states of d{3z{2}-r{2}} symmetry near the Fermi level that discloses their participation in the occurring electron-correlation phenomena and provides insight into mechanism of superconductivity in oxopnictides.
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Affiliation(s)
- M G Holder
- Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany
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20
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de la Cruz C, Hu WZ, Li S, Huang Q, Lynn JW, Green MA, Chen GF, Wang NL, Mook HA, Si Q, Dai P. Lattice distortion and magnetic quantum phase transition in CeFeAs(1-x)P(x)O. PHYSICAL REVIEW LETTERS 2010; 104:017204. [PMID: 20366390 DOI: 10.1103/physrevlett.104.017204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Indexed: 05/29/2023]
Abstract
We use neutron diffraction to study the structural and magnetic phase diagram of CeFeAs(1-x)P(x)O. We find that replacing the larger arsenic with smaller phosphorus in CeFeAs(1-x)P(x)O simultaneously suppresses the AFM order and orthorhombic distortion near x=0.4, thus suggesting the presence of a magnetic quantum critical point. Our detailed structural analysis reveals that the pnictogen height is an important controlling parameter for their electronic and magnetic properties, and may play an important role in electron pairing and superconductivity of these materials.
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Affiliation(s)
- Clarina de la Cruz
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
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Dai J, Si Q, Zhu JX, Abrahams E. Iron pnictides as a new setting for quantum criticality. Proc Natl Acad Sci U S A 2009; 106:4118-21. [PMID: 19273850 PMCID: PMC2657431 DOI: 10.1073/pnas.0900886106] [Citation(s) in RCA: 157] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2008] [Indexed: 11/18/2022] Open
Abstract
Two major themes in the physics of condensed matter are quantum critical phenomena and unconventional superconductivity. These usually occur in the context of competing interactions in systems of strongly correlated electrons. All this interesting physics comes together in the behavior of the recently discovered iron pnictide compounds that have generated enormous interest because of their moderately high-temperature superconductivity. The ubiquity of antiferromagnetic ordering in their phase diagrams naturally raises the question of the relevance of magnetic quantum criticality, but the answer remains uncertain both theoretically and experimentally. Here, we show that the undoped iron pnictides feature a unique type of magnetic quantum critical point, which results from a competition between electronic localization and itinerancy. Our theory provides a mechanism to understand the experimentally observed variation of the ordered moment among the undoped iron pnictides. We suggest P substitution for As in the undoped iron pnictides as a means to access this example of magnetic quantum criticality in an unmasked fashion. Our findings point to the iron pnictides as a much-needed setting for quantum criticality, one that offers a unique set of control parameters.
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Affiliation(s)
- Jianhui Dai
- Zhejiang Institute of Modern Physics, Zhejiang University, Hangzhou 310027, China
| | - Qimiao Si
- Department of Physics and Astronomy, Rice University, Houston, TX 77005
| | - Jian-Xin Zhu
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545; and
| | - Elihu Abrahams
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, NJ 08855
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22
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Bondino F, Magnano E, Malvestuto M, Parmigiani F, McGuire MA, Sefat AS, Sales BC, Jin R, Mandrus D, Plummer EW, Singh DJ, Mannella N. Evidence for strong itinerant spin fluctuations in the normal state of CeFeAsO0.89F0.11 iron-oxypnictide superconductors. PHYSICAL REVIEW LETTERS 2008; 101:267001. [PMID: 19113783 DOI: 10.1103/physrevlett.101.267001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2008] [Indexed: 05/27/2023]
Abstract
The electronic structure in the normal state of CeFeAsO0.89F0.11 oxypnictide superconductors has been investigated with x-ray absorption and photoemission spectroscopy. All of the data exhibit signatures of Fe d-electron itinerancy. Exchange multiplets appearing in the Fe 3s core level indicate the presence of itinerant spin fluctuations. These findings suggest that the underlying physics and the origin of superconductivity in these materials are likely to be quite different from those of the cuprate high-temperature superconductors. These materials provide opportunities for elucidating the role of magnetic fluctuations in high-temperature superconductivity.
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Affiliation(s)
- F Bondino
- CNR-INFM, Laboratorio Nazionale TASC, S.S. 14, km 163.5, 1-34012 Trieste, Italy
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