Transition from the diamagnetic insulator to ferromagnetic metal in La.sub.1-x./sub.Sr.sub.x./sub.CoO.sub.3./sub..

0353298 - FZÚ 2011 RIV NL eng J - Journal Article
Knížek, Karel - Jirák, Zdeněk - Hejtmánek, Jiří - Novák, Pavel
Transition from the diamagnetic insulator to ferromagnetic metal in La_1-xSr_xCoO₃.
Journal of Magnetism and Magnetic Materials. Roč. 322, 9-12 (2010), s. 1221-1223. ISSN 0304-8853. E-ISSN 1873-4766
R&D Projects: GA AV ČR IAA100100611
Institutional research plan: CEZ:AV0Z10100521
Keywords : LnCoO₃ * GGA+U calculation * spin states transition
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.689, year: 2010

We have analyzed, using the theoretical GGA+U calculations, different configurations of spin states (LS, IS and HS Co3+) and proposed a model that accounts for magnetic and electric transport properties of perovskite cobaltites upon doping by charge carriers. In particular, it appears that the compositional transition from the diamagnetic LS phase of LaCoO3 to the ferromagnetic metallic IS phase in La1-xSrxCoO3 (x > 0.2) involves the same mechanisms as the high-temperature transition in pure LaCoO3. The process occurs gradually via a phase-separated state, where metallic IS domains stabilized through a charge transfer between Co4+ and Co3+ neighbors coexist with the Co4+ poor regions in the LS ground state (or, at higher temperatures, in mixed LS/HS state). This phase separation vanishes when doping in La1-xSrxCoO3 reaches x ~ 0.2, and a uniform IS phase, analogous to that in pure LaCoO3 in the high-temperature limit, is established.
Permanent Link: http://hdl.handle.net/11104/0192582