1
|
Min L, Barber JP, Wang Y, Gayathri Ayyagari SV, Niculescu GE, Krysko E, Bejger GR, Miao L, Lee SH, Zhang Q, Alem N, Rost CM, Mao Z. High Entropy Protected Sharp Magnetic Transitions in Highly Disordered Spinel Ferrites. J Am Chem Soc 2024; 146:24320-24329. [PMID: 39163142 DOI: 10.1021/jacs.4c04765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2024]
Abstract
How disorder affects magnetic ordering is always an intriguing question, and it becomes even more interesting in the recently rising high entropy oxides due to the extremely high disorder density. However, due to the lack of high-quality single crystal samples, the strong compositional disorder effect on magnetic transition has not been deeply investigated. In this work, we have successfully synthesized high-quality single crystalline high entropy spinel ferrites (Mg0.2Mn0.2Fe0.2Co0.2Ni0.2)xFe3-xO4. Our findings from high-temperature magnetization and neutron diffraction experiments showed ferrimagnetic transitions at 748, 694, and 674 K for x values of 1, 1.5, and 1.8, respectively. Notably, the magnetic transition almost showed no broadening for x values of 1 and 1.5, compared to Fe3O4. Extended X-ray absorption fine structure measurements provided insights into the elemental distribution among the octahedral and tetrahedral sites. The random distribution of elements across these sites reduced the formation of local clusters and short-range orders, enhancing sample homogeneity and preserving the sharpness of the magnetic transition, despite bond length variation. Our study not only marks the first successful synthesis of an HEO bulk single crystal exhibiting long-range magnetic order but also sheds light on the interaction between high configurational entropy and magnetic orderings. This opens new avenues for future research and applications of magnetic high entropy oxides.
Collapse
Affiliation(s)
- Lujin Min
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - John P Barber
- Department of Physics & Astronomy, James Madison University, Harrisonburg, Virginia 22807, United States
- Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Yu Wang
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- 2D Crystal Consortium, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Sai Venkata Gayathri Ayyagari
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Gabriela E Niculescu
- Department of Physics & Astronomy, James Madison University, Harrisonburg, Virginia 22807, United States
| | - Evan Krysko
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Gerald R Bejger
- Department of Physics & Astronomy, James Madison University, Harrisonburg, Virginia 22807, United States
- Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Leixin Miao
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Seng Huat Lee
- 2D Crystal Consortium, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Qiang Zhang
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States
| | - Nasim Alem
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Christina M Rost
- Department of Physics & Astronomy, James Madison University, Harrisonburg, Virginia 22807, United States
- Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Zhiqiang Mao
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| |
Collapse
|
2
|
Schröter NBM, Robredo I, Klemenz S, Kirby RJ, Krieger JA, Pei D, Yu T, Stolz S, Schmitt T, Dudin P, Kim TK, Cacho C, Schnyder A, Bergara A, Strocov VN, de Juan F, Vergniory MG, Schoop LM. Weyl fermions, Fermi arcs, and minority-spin carriers in ferromagnetic CoS 2. SCIENCE ADVANCES 2020; 6:eabd5000. [PMID: 33355138 PMCID: PMC11206217 DOI: 10.1126/sciadv.abd5000] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 11/05/2020] [Indexed: 06/12/2023]
Abstract
Magnetic Weyl semimetals are a newly discovered class of topological materials that may serve as a platform for exotic phenomena, such as axion insulators or the quantum anomalous Hall effect. Here, we use angle-resolved photoelectron spectroscopy and ab initio calculations to discover Weyl cones in CoS2, a ferromagnet with pyrite structure that has been long studied as a candidate for half-metallicity, which makes it an attractive material for spintronic devices. We directly observe the topological Fermi arc surface states that link the Weyl nodes, which will influence the performance of CoS2 as a spin injector by modifying its spin polarization at interfaces. In addition, we directly observe a minority-spin bulk electron pocket in the corner of the Brillouin zone, which proves that CoS2 cannot be a true half-metal.
Collapse
Affiliation(s)
- Niels B M Schröter
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
| | - Iñigo Robredo
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain
- Condensed Matter Physics Department, University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
| | - Sebastian Klemenz
- Department of Chemistry, Princeton University, Princeton, NJ 08540, USA
| | - Robert J Kirby
- Department of Chemistry, Princeton University, Princeton, NJ 08540, USA
| | - Jonas A Krieger
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Laboratorium für Festkörperphysik, ETH Zurich, CH-8093 Zurich, Switzerland
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Ding Pei
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Tianlun Yu
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
- Advanced Materials Laboratory, State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Samuel Stolz
- EMPA, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Condensed Matter Physics, Station 3, EPFL, 1015 Lausanne, Switzerland
| | - Thorsten Schmitt
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | | | | | | | - Andreas Schnyder
- Max Planck Institute for Solid State Research, 70569, Stuttgart, Germany
| | - Aitor Bergara
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain
- Condensed Matter Physics Department, University of the Basque Country UPV/EHU, 48080 Bilbao, Spain
- Centro de Física de Materiales, Centro Mixto CSIC -UPV/EHU, 20018 Donostia, Spain
| | - Vladimir N Strocov
- Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Fernando de Juan
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Maia G Vergniory
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Spain.
- IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Leslie M Schoop
- Department of Chemistry, Princeton University, Princeton, NJ 08540, USA.
| |
Collapse
|
3
|
Walter J, Voigt B, Day-Roberts E, Heltemes K, Fernandes RM, Birol T, Leighton C. Voltage-induced ferromagnetism in a diamagnet. SCIENCE ADVANCES 2020; 6:eabb7721. [PMID: 32832693 PMCID: PMC7439324 DOI: 10.1126/sciadv.abb7721] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 06/12/2020] [Indexed: 05/29/2023]
Abstract
Increasingly impressive demonstrations of voltage-controlled magnetism have been achieved recently, highlighting potential for low-power data processing and storage. Magnetoionic approaches appear particularly promising, electrolytes and ionic conductors being capable of on/off control of ferromagnetism and tuning of magnetic anisotropy. A clear limitation, however, is that these devices either electrically tune a known ferromagnet or electrically induce ferromagnetism from another magnetic state, e.g., antiferromagnetic. Here, we demonstrate that ferromagnetism can be voltage-induced even from a diamagnetic (zero-spin) state suggesting that useful magnetic phases could be electrically induced in "nonmagnetic" materials. We use ionic liquid-gated diamagnetic FeS2 as a model system, showing that as little as 1 V induces a reversible insulator-metal transition by electrostatic surface inversion. Anomalous Hall measurements then reveal electrically tunable surface ferromagnetism at up to 25 K. Density functional theory-based modeling explains this in terms of Stoner ferromagnetism induced via filling of a narrow e g band.
Collapse
Affiliation(s)
- Jeff Walter
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Physics, Augsburg University, Minneapolis, MN 55454, USA
| | - Bryan Voigt
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ezra Day-Roberts
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kei Heltemes
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Physics, Augsburg University, Minneapolis, MN 55454, USA
| | - Rafael M. Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Turan Birol
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| | - Chris Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA
| |
Collapse
|
4
|
Salas UA, Fourati I, Juraszek J, Richomme F, Pelloquin D, Maignan A, Hébert S. Impact of the iron substitution on the thermoelectric properties of Co 1- xFe xS 2 ( x ≤ 0.30). PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20180337. [PMID: 31280719 PMCID: PMC6635634 DOI: 10.1098/rsta.2018.0337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/24/2019] [Indexed: 06/09/2023]
Abstract
The strong interplay between magnetism and transport can tune the thermoelectric properties in chalcogenides and oxides. In the case of ferromagnetic CoS2 pyrite, it was previously shown that the power factor is large at room temperature, reaching 1 mW m-1 K-2 and abruptly increases for temperatures below the Curie transition ( TC), an increase potentially due to a magnonic effect on the Seebeck ( S) coefficient. The too large thermal conductivity approximately equal to 10.5 W m-1 K-1 at room temperature prevents this pyrite from being a good thermoelectric material. In this work, samples belonging to the Co1- xFe xS2 pyrite family ( x = 0, 0.15 and 0.30) have thus been investigated in order to modify the thermal properties by the introduction of disorder on the Co site. We show here that the thermal conductivity can indeed be reduced by such a substitution, but that this substitution predominantly induces a reduction of the electronic part of the thermal conductivity and not of the lattice part. Interestingly, the magnonic contribution to S below TC disappears as x increases, while at high T, S tends to a very similar value (close to -42 µV K-1) for all the samples investigated. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'.
Collapse
Affiliation(s)
- Ulises Acevedo Salas
- Normandie université, ENSICAEN, UNICAEN, CNRS, CRISMAT UMR6508, 14000 Caen, France
| | - Ismail Fourati
- Normandie université, UNIROUEN, INSA Rouen, CNRS, GPM UMR6634, 76000 Rouen, France
| | - Jean Juraszek
- Normandie université, UNIROUEN, INSA Rouen, CNRS, GPM UMR6634, 76000 Rouen, France
| | - Fabienne Richomme
- Normandie université, UNIROUEN, INSA Rouen, CNRS, GPM UMR6634, 76000 Rouen, France
| | - Denis Pelloquin
- Normandie université, ENSICAEN, UNICAEN, CNRS, CRISMAT UMR6508, 14000 Caen, France
| | - Antoine Maignan
- Normandie université, ENSICAEN, UNICAEN, CNRS, CRISMAT UMR6508, 14000 Caen, France
| | - Sylvie Hébert
- Normandie université, ENSICAEN, UNICAEN, CNRS, CRISMAT UMR6508, 14000 Caen, France
| |
Collapse
|
5
|
Houari A, Blöchl PE. Density functional study of half-metallicity and spin polarization in Fe 1-x T x S 2 with T = Mn,Ni. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:305501. [PMID: 29897339 DOI: 10.1088/1361-648x/aacc5a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Alloying effects by Mn and Ni substitution on FeS2 have been studied using density-functional calculations. Standard generalized gradient approximation (GGA) and local hybrid functional have been utilized to account for exchange-correlations. The alloys Fe1-x T x S2 with T = Mn,Ni have been investigated for concentrations [Formula: see text] together with the ground states of the pure compounds. The electronic structure is discussed with the main goal to identify candidates for ferromagnetic half-metals, which are of interest for spintronics applications. Depending on the used calculation framework, interesting candidates have been found at different concentrations. However, at mean concentration of the Mn-doping and low concentration for Ni-doping, both GGA and hybrid functional agree to predict half-metallic character. For the Mn alloys we also note the proximity to a low-spin to high spin transition.
Collapse
Affiliation(s)
- Abdesalem Houari
- Theoretical Physics Laboratory, Department of Physics, University of Bejaia, Bejaia, Algeria
| | | |
Collapse
|
6
|
Gabold H, Luan Z, Paul N, Opel M, Müller-Buschbaum P, Law M, Paul A. Structural and magnetic properties of cobalt iron disulfide (Co xFe 1-xS 2) nanocrystals. Sci Rep 2018; 8:4835. [PMID: 29556096 PMCID: PMC5859158 DOI: 10.1038/s41598-018-22996-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 03/05/2018] [Indexed: 12/04/2022] Open
Abstract
We report on synthesis and investigation of nanocrystalline cobalt-iron-pyrites with an emphasis on nanocrystal structure, morphology and magnetic behavior. The nanocrystals (NCs) were 5-25 nm in diameter as characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). With an increase in Fe fraction, X-ray diffraction and small-angle-X-ray scattering (SAXS) showed a systematic decrease in lattice constant, primary grain/NC size (15 to 7 nm), and nanoparticle (NP) size (70 to 20 nm), respectively. The temperature dependence of the DC magnetization and AC susceptibility versus frequency revealed a number of magnetic phases in Co x Fe1-xS2. Samples with x = 1 and x = 0.875-0.625 showed evidence of superspin glass (SSG) behavior with embedded ferromagnetic (FM) clusters of NPs. For x = 0.5, samples retained their mixed phases, but showed superparamagnetic (SPM) behavior with antiferromagnetic clusters suppressing magnetic dipolar interactions. Below x = 0.5, the pyrites show increasing paramagnetic character. We construct a phase diagram, which can be understood in terms of competition between the various dipolar, exchange, inter- and intracluster interactions. Our results suggest that NC size and shape can be tuned to engineer spin-polarized ferromagnetism of n-doped iron pyrite.
Collapse
Affiliation(s)
- Henrik Gabold
- Technische Universität München, Physik-Department, Lehrstuhl für Neutronenstreuung, James-Franck-Strasse 1, D-85748, Garching, Germany
| | - Zhongyue Luan
- Department of Chemical Engineering & Materials Science, University of California Irvine, Irvine, CA, 92697, USA
| | - Neelima Paul
- Heinz Maier-Leibnitz (MLZ), Technische Universität München, D-85748, Garching, Germany
| | - Matthias Opel
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748, Garching, Germany
| | - Peter Müller-Buschbaum
- Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, James-Franck-Str. 1, D-85748, Garching, Germany
| | - Matt Law
- Department of Chemical Engineering & Materials Science, University of California Irvine, Irvine, CA, 92697, USA
- Department of Chemistry, University of California Irvine, Irvine, CA, 92697, USA
| | - Amitesh Paul
- Technische Universität München, Physik-Department, Lehrstuhl für Neutronenstreuung, James-Franck-Strasse 1, D-85748, Garching, Germany.
| |
Collapse
|
7
|
Zhang X, Wu N, Manno M, Leighton C, Vescovo E, Dowben PA. Resonant photoemission and spin polarization of Co(1-x)Fe(x)S(2). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:012001. [PMID: 23160359 DOI: 10.1088/0953-8984/25/1/012001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The valence band occupied state electronic structure of Co(1-x)Fe(x)S(2) in the region of the Fe/Co 3d bands has been investigated using photoemission and spin-polarized photoemission. As measured by using spin-polarized ultraviolet photoemission, the surface Fermi level spin polarization of Co(1-x)Fe(x)S(2) thin films at 50 K, specifically at x = 0, 0.05, 0.10 and 0.15, was found to be much reduced compared to that of the bulk. The spin polarization nonetheless increases with Fe concentration. The resonant photoemission spectroscopy provides evidence that S bands have a strong resonance at the photon energy corresponding to the Co 2p core level, indicating strong hybridization between Co and S bands in Co(1-x)Fe(x)S(2) (at small x). Similar evidence exists for Fe hybridization with the S bands.
Collapse
Affiliation(s)
- Xin Zhang
- Nebraska Center for Materials and Nanoscience, Department of Physics and Astronomy, University of Nebraska-Lincoln, 68588-0299, USA
| | | | | | | | | | | |
Collapse
|
8
|
Utfeld C, Giblin SR, Taylor JW, Duffy JA, Shenton-Taylor C, Laverock J, Dugdale SB, Manno M, Leighton C, Itou M, Sakurai Y. Bulk spin polarization of Co(1-x)Fe(x)S2. PHYSICAL REVIEW LETTERS 2009; 103:226403. [PMID: 20366116 DOI: 10.1103/physrevlett.103.226403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Indexed: 05/29/2023]
Abstract
We report on a new method to determine the degree of bulk spin polarization in single crystal Co(1-x)Fe(x)S2 by modeling magnetic Compton scattering with ab initio calculations. Spin-dependent Compton profiles were measured for CoS2 and Co0.9Fe0.1S2. The ab initio calculations were then refined by rigidly shifting the bands to provide the best fit between the calculated and experimental directional profiles for each sample. The bulk spin polarizations, P, corresponding to the spin-polarized density of states at the Fermi level, were then extracted from the refined calculations. The values were found to be P=-72+/-6% and P=18+/-7% for CoS2 and Co0.9Fe0.1S2, respectively. Furthermore, determinations of P weighted by the Fermi velocity (v(F) or v(F)2) were obtained, permitting a rigorous comparison with other experimental data and highlighting the experimental dependence of P on v(F).
Collapse
Affiliation(s)
- C Utfeld
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|