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Impurity-Induced Spin-State Crossover in La0.8Sr0.2Co1−xAlxO3

Impurity-Induced Spin-State Crossover in La0.8Sr0.2Co1−xAlxO3

Authors :
Ichiro Terasaki
Masamichi Ikuta
Takafumi D. Yamamoto
Hiroki Taniguchi
Source :
Crystals, Vol 8, Iss 11, p 411 (2018)
Publication Year :
2018
Publisher :
MDPI AG, 2018.

Abstract

We have prepared a set of polycrystalline samples of La 0.8 Sr 0.2 Co 1 − x Al x O 3 ( 0 ≤ x ≤ 0.2 ), and have measured the magnetization as functions of temperature and magnetic field. We find that the average spin number per Co ion ( S Co ) evaluated from the room-temperature susceptibility is around 1.2⁻1.3 and independent of x. However, we further find that S Co evaluated from the saturation magnetization at 2 K is around 0.3⁻0.7, and decreases dramatically with x. This naturally indicates that a significant fraction of the Co 3 + ions experience a spin-state crossover from the intermediate- to low-spin state with decreasing temperature in the Al-substituted samples. This spin-state crossover also explains the resistivity and the thermopower consistently. In particular, we find that the thermopower is anomalously enhanced by the Al substitution, which can be consistently explained in terms of an extended Heikes formula.

Details

Language :
English
ISSN :
20734352
Volume :
8
Issue :
11
Database :
Directory of Open Access Journals
Journal :
Crystals
Publication Type :
Academic Journal
Accession number :
edsdoj.19968f1932b49778bee6e2ab0178f56
Document Type :
article
Full Text :
https://doi.org/10.3390/cryst8110411