Comprehensive investigation of crystallographic, spin-electronic and magnetic structure of (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4: Unraveling the suppression of configuration entropy in high entropy oxides
Sarkar, Abhishek; Eggert, Benedikt; Witte, Ralf; Lill, Johanna; Velasco, Leonardo; Wang, Qingsong; Sonar, Janhavika; Ollefs, Katharina; Bhattacharya, Subramshu S.; Brand, Richard A.; Wende, Heiko; de Groot, Frank M.F.; Clemens, Oliver; Hahn, Horst; Kruk, Robert
(2022) Acta Materialia, volume 226, pp. 1 - 12
(Article)
Abstract
High entropy oxides (HEOs) are a rapidly emerging class of functional materials consisting of multiple principal cations. The original paradigm of HEOs assumes cationic occupations with the highest possible configurational entropy allowed by the composition and crystallographic structure. However, the fundamental question remains on the actual degree of configurational disorder
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in HEOs, especially, in systems with a low enthalpy barriers for cation anti-site mixing. Considering the experimental limitations due to the presence of multiple principal cations in HEOs, here we utilize a robust and cross-referenced characterization approach using soft X-ray magnetic circular dichroism, hard X-ray absorption spectroscopy, Mössbauer spectroscopy, neutron powder diffraction and SQUID magnetometry to study the competition between crystal field stabilization energy and configurational entropy governing the cation occupation in a spinel HEO (S-HEO), (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4. In contrast to the previous studies, the derived complete structural and spin-electronic model, (Co0.6Fe0.4)(Cr0.3Fe0.1Mn0.3Ni0.3)2O4, highlights a significant deviation from the hitherto assumed paradigm of entropy-driven non-preferential distribution of cations in HEOs. An immediate correlation of this result can be drawn with bulk as well as the local element specific magnetic properties, which are intrinsically dictated by cationic occupations in spinels. The real local lattice picture presented here provides an alternate viewpoint on ionic arrangement in HEOs, which is of fundamental interest for predicting and designing their structure-dependent functionalities.
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Keywords: High entropy spinel, Preferential cationic occupation, X-ray magnetic circular dichroism, Mössbauer spectroscopy, Neutron diffraction, preferential cationic occupation, Taverne, Electronic, Optical and Magnetic Materials, Ceramics and Composites, Metals and Alloys, Polymers and Plastics
ISSN: 1359-6454
Publisher: Elsevier Limited
Note: Funding Information: We acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG) project HA 1344/43-2 (A.S. and H.H.) and WE 2623/14-2 Project-ID 322462997 (B.E. and H.W.). L.V. acknowledges Karlsruhe Nano Micro Facility (KNMF) for the use of the TEM. J.S. acknowledges funding support from DAAD/IIT-Master-Sandwich-Programm 2018-19. We thank support from Eugen Weschke and Helmholtz-Zentrum Berlin for the beam time at the beamline UE46 PGM_1 (proposal 192-08578-ST/R), Qiang Zhang, Melanie Kirkham and Oak Ridge National Laboratory for beam time at BL-11A POWGEN (proposal IPTS-22136.1), Ruidy Nemausat and DESY (Hamburg, Germany) for the beam time at PETRA III P65 (proposal 20190485). Funding Information: We acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG) project HA 1344/43-2 (A.S. and H.H.) and WE 2623/14-2 Project-ID 322462997 (B.E. and H.W.). L.V. acknowledges Karlsruhe Nano Micro Facility (KNMF) for the use of the TEM. J.S. acknowledges funding support from DAAD/IIT-Master-Sandwich-Programm 2018-19. We thank support from Eugen Weschke and Helmholtz-Zentrum Berlin for the beam time at the beamline UE46 PGM_1 (proposal 192-08578-ST/R), Qiang Zhang, Melanie Kirkham and Oak Ridge National Laboratory for beam time at BL-11A POWGEN (proposal IPTS-22136.1), Ruidy Nemausat and DESY (Hamburg, Germany) for the beam time at PETRA III P65 (proposal 20190485). Publisher Copyright: © 2021 Acta Materialia Inc.
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