skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)

Abstract

We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo(2)As(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 eleetron) change in the population of the 3d orbitals. The mixed valence state of En observed in the high-pressure (HP) form of EuCo2As2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. The results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material's properties via involvement of strongly correlated electrons.

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division; Russian Science Foundation
OSTI Identifier:
1252701
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
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)
Country of Publication:
United States
Language:
English

Citation Formats

Tan, Xiaoyan, Fabbris, Gilberto, Haskel, Daniel, Yaroslavtsev, Alexander A., Cao, H., Thompson, Corey M., Kovnir, Kirill, Menushenkov, Alexey P., Chernikov, Roman V., Garlea, V. Ovidiu, and Shatruk, Michael. A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca). United States: N. p., 2016. Web. doi:10.1021/jacs.5b12659.
Tan, Xiaoyan, Fabbris, Gilberto, Haskel, Daniel, Yaroslavtsev, Alexander A., Cao, H., Thompson, Corey M., Kovnir, Kirill, Menushenkov, Alexey P., Chernikov, Roman V., Garlea, V. Ovidiu, & Shatruk, Michael. A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca). United States. doi:10.1021/jacs.5b12659.
Tan, Xiaoyan, Fabbris, Gilberto, Haskel, Daniel, Yaroslavtsev, Alexander A., Cao, H., Thompson, Corey M., Kovnir, Kirill, Menushenkov, Alexey P., Chernikov, Roman V., Garlea, V. Ovidiu, and Shatruk, Michael. Wed . "A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)". United States. doi:10.1021/jacs.5b12659.
@article{osti_1252701,
title = {A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)},
author = {Tan, Xiaoyan and Fabbris, Gilberto and Haskel, Daniel and Yaroslavtsev, Alexander A. and Cao, H. and Thompson, Corey M. and Kovnir, Kirill and Menushenkov, Alexey P. and Chernikov, Roman V. and Garlea, V. Ovidiu and Shatruk, Michael},
abstractNote = {We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo(2)As(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 eleetron) change in the population of the 3d orbitals. The mixed valence state of En observed in the high-pressure (HP) form of EuCo2As2 exhibits a remarkable stability, achieving the average oxidation state of +2.25 at 12.6 GPa. In the case of CaCo2As2, substituting even 10% of Eu or La into the Ca site causes ferromagnetic ordering of Co moments. Similar to HP-EuCo2As2, the itinerant 3d ferromagnetism emerges from electronic doping into the Co layer because of chemical compression of Eu sites in Ca0.9Eu0.1Co1.91As2 or direct electron doping in Ca0.85La0.15Co1.89As2. The results reported herein demonstrate the general possibility of amplifying minor localized electronic effects to achieve major changes in material's properties via involvement of strongly correlated electrons.},
doi = {10.1021/jacs.5b12659},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 8,
volume = 138,
place = {United States},
year = {2016},
month = {3}
}

Works referencing / citing this record:

CSD 1470297: Experimental Crystal Structure Determination: Non-CSD Structure
dataset, March 2016


CSD 1470298: Experimental Crystal Structure Determination: Non-CSD Structure
dataset, March 2016