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

Xiaoyan Tan; Gilberto Fabbris; Daniel Haskel; Alexander A. Yaroslavtsev; Huibo Cao; Corey M. Thompson; Kirill Kovnir; Alexey P. Menushenkov; Roman V. Chernikov; V. Ovidiu Garlea; Michael Shatruk

doi:10.1021/jacs.5b12659

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

Xiaoyan Tan, Gilberto Fabbris, Daniel Haskel, Alexander A. Yaroslavtsev, Huibo Cao, Corey M. Thompson, Kirill Kovnir, Alexey P. Menushenkov, Roman V. Chernikov, V. Ovidiu Garlea, Michael Shatruk

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Abstract

We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo₂As₂ (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 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 Ca_0.9Eu_0.1Co_1.91As₂ or direct electron doping in Ca_0.85La_0.15Co_1.89As₂. 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.

Original language	English
Pages (from-to)	2724-2731
Number of pages	8
Journal	Journal of the American Chemical Society
Volume	138
Issue number	8
DOIs	https://doi.org/10.1021/jacs.5b12659
State	Published - Mar 2 2016

Funding

This work was supported by the National Science Foundation (Award DMR-1507233 to M.S.). The work at the Oak Ridge National Laboratory was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). The use of the Advanced Photon Source at Argonne National Laboratory was supported by U.S. DOE under Contract No. DEAC02?06CH11357. A.P.M. and A.A.Y. thank the Russian Scientific Foundation (project 14?22?00098) for support. We acknowledge Helmholtz-Zentrum Berlin for providing the beamtime at the BESSY-II storage ring, Dr. Ivo Zizak and Dr. Dirk Wallacher for support during the experiment.

Funders	Funder number
Office of Basic Energy Sciences
Russian Scientific Foundation	00098
Scientific User Facilities Division
U.S. DOE	06CH11357
National Science Foundation	DMR-1507233, 1507233
U.S. Department of Energy
Helmholtz-Zentrum Berlin für Materialien und Energie

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10.1021/jacs.5b12659

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Tan, X., Fabbris, G., Haskel, D., Yaroslavtsev, A. A., Cao, H., Thompson, C. M., Kovnir, K., Menushenkov, A. P., Chernikov, R. V., Garlea, V. O., & Shatruk, M. (2016). A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo₂As₂ (A = Eu and Ca). Journal of the American Chemical Society, 138(8), 2724-2731. https://doi.org/10.1021/jacs.5b12659

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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 ACo2As2 (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 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.",

author = "Xiaoyan Tan and Gilberto Fabbris and Daniel Haskel and Yaroslavtsev, {Alexander A.} and Huibo Cao and Thompson, {Corey M.} and Kirill Kovnir and Menushenkov, {Alexey P.} and Chernikov, {Roman V.} and Garlea, {V. Ovidiu} and Michael Shatruk",

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doi = "10.1021/jacs.5b12659",

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Tan, X, Fabbris, G, Haskel, D, Yaroslavtsev, AA, Cao, H, Thompson, CM, Kovnir, K, Menushenkov, AP, Chernikov, RV, Garlea, VO & Shatruk, M 2016, 'A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo₂As₂ (A = Eu and Ca)', Journal of the American Chemical Society, vol. 138, no. 8, pp. 2724-2731. https://doi.org/10.1021/jacs.5b12659

TY - JOUR

T1 - A Transition from Localized to Strongly Correlated Electron Behavior and Mixed Valence Driven by Physical or Chemical Pressure in ACo2As2 (A = Eu and Ca)

AU - Tan, Xiaoyan

AU - Fabbris, Gilberto

AU - Haskel, Daniel

AU - Yaroslavtsev, Alexander A.

AU - Cao, Huibo

AU - Thompson, Corey M.

AU - Kovnir, Kirill

AU - Menushenkov, Alexey P.

AU - Chernikov, Roman V.

AU - Garlea, V. Ovidiu

AU - Shatruk, Michael

PY - 2016/3/2

Y1 - 2016/3/2

N2 - We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo2As2 (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 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.

AB - We demonstrate that the action of physical pressure, chemical compression, or aliovalent substitution in ACo2As2 (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 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.

UR - http://www.scopus.com/inward/record.url?scp=84959487341&partnerID=8YFLogxK

U2 - 10.1021/jacs.5b12659

DO - 10.1021/jacs.5b12659

M3 - Article

AN - SCOPUS:84959487341

SN - 0002-7863

VL - 138

SP - 2724

EP - 2731

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 8

ER -

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

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