Universität zu Köln

Jia, Ting, Wu, Hua ORCID: 0000-0003-1280-202X, Zhang, Guoren, Zhang, Xiaoli, Guo, Ying, Zeng, Zhi and Lin, H. Q. (2010). Spin states of Co ions in La1.5Ca0.5CoO4 from first principles. Phys. Rev. B, 82 (20). COLLEGE PK: AMER PHYSICAL SOC. ISSN 1098-0121

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Abstract

The spin states and electronic structure of layered perovskite La1.5Ca0.5CoO4 are investigated using full-potential linearized augmented plane-wave method. All the computational results indicate that the Co2+ ion is in a high-spin (HS, t(2g)(5)e(g)(2)) state and the Co3+ in a low-spin (LS, t(2g)(6)) state. The Co2+ t(2g) orbitals with a small crystal-field splitting are mixed by spin-orbit coupling, which accounts for the observed easy in-plane magnetism. The nonmagnetic LS-Co3+ state, which is stabilized by a strong crystal field, provides a natural explanation for the observed low magnetic ordering temperature and a spin-blockade phenomenon of the electron hopping. Furthermore, we find that the intermediate-spin (IS, t(2g)(5)e(g)(1)) state of Co3+ has a large multiplet splitting. But the lowest-lying IS state of Co3+ is still higher in energy than the LS ground state by a few hundred millielectron volts and the HS state of Co3+ is even less stable, both in sharp contrast to a recent experimental study which suggested the HS+IS mixed Co3+ ground state. We note that either the IS-Co3+ or HS-Co3+ states or their mixture would produce a wrong out-of-plane magnetic anisotropy and a much higher magnetic-ordering temperature than observed. Thus, the present work sheds light on this material concerning its electronic and magnetic structure, and it would stimulate different experiments to settle this intriguing spin-state issue.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Jia, Ting UNSPECIFIED UNSPECIFIED UNSPECIFIED Wu, Hua UNSPECIFIED orcid.org/0000-0003-1280-202X UNSPECIFIED Zhang, Guoren UNSPECIFIED UNSPECIFIED UNSPECIFIED Zhang, Xiaoli UNSPECIFIED UNSPECIFIED UNSPECIFIED Guo, Ying UNSPECIFIED UNSPECIFIED UNSPECIFIED Zeng, Zhi UNSPECIFIED UNSPECIFIED UNSPECIFIED Lin, H. Q. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-492701
DOI:	10.1103/PhysRevB.82.205107
Journal or Publication Title:	Phys. Rev. B
Volume:	82
Number:	20
Date:	2010
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	1098-0121
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PHASE-TRANSITIONS; LACOO3; MAGNETORESISTANCE Multiple languages Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/49270