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Title: A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo 2As 2 (A = Eu and Ca)

In this paper, we demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo 2As 2 (A = Eu and Ca) has a general consequence of causing these antiferromagnetic materials to become ferromagnets. In all cases, the mixed valence triggered at the electropositive A site results in the increase of the Co 3d density of states at the Fermi level. Remarkably, the dramatic alteration of magnetic behavior results from the very minor (<0.15 electron) change in the population of the 3d orbitals. The mixed valence state of Eu observed in the high-pressure (HP) form of EuCo 2As 2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo 2As 2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo 2As 2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca 0.9Eu 0.1Co 1.91As 2 or direct electron doping in Ca 0.85La 0.15Co 1.89As 2. Finally, the results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes inmore » material’s properties via involvement of strongly correlated electrons.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [1] ;  [6] ;  [7] ;  [5] ;  [1]
  1. Florida State Univ., Tallahassee, FL (United States). Dept. of Chemistry and Biochemistry
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source; Washington Univ., St. Louis, MO (United States). Dept. of Physics
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source
  4. National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Inst.), Moscow (Russian Federation); European X-ray Free-Electron Laser (XFEL), Hamburg (Germany)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  6. National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Inst.), Moscow (Russian Federation)
  7. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Photon Science
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-06CH11357; DMR-1507233
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 8; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Florida State Univ., Tallahassee, FL (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Contributing Orgs:
Washington Univ., St. Louis, MO (United States); National Research Nuclear Univ. MEPhI (Moscow Engineering Physics Inst.), Moscow (Russian Federation); European X-ray Free-Electron Laser (XFEL), Hamburg (Germany); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1335338