Phase evolution of layered cobalt oxides versus varying corrugation of the 
cobalt-oxygen basal plane

Wu, H.

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Phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen basal plane

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Wu, H.
Max Planck Institute for the Physics of Complex Systems, Max Planck Society;

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引用

Wu, H. (2002). Phase evolution of layered cobalt oxides versus varying corrugation of the cobalt-oxygen basal plane. European Physical Journal B, 30(4), 501-510. Retrieved from http://link.springer.de/link/service/journals/10051/bibs/2030004/20300501.htm.

引用: https://hdl.handle.net/11858/00-001M-0000-002B-3697-1

要旨

A general spin-state model and a qualitative physical picture have been proposed for a class of lately synthesized layered cobalt oxides (LCOs) by means of density functional calculations. As the plane corrugation of the cobalt-oxygen layer decreases, the LCOs evolve from a high-spin (HS) superexchange-coupled antiferromagnetic (AFM) insulator to an almost-HS AFM/ferromagnetic (FM) competing system where the FM coupling is mediated via the p-d exchange by an increasing amount of delocalized pdsigma holes having mainly the planar 0 2p character. It is tentatively suggested that the delocalized holes more than 0.3 per CoO2 basal square are likely necessary for the insulator-metal and/or AFM-FM transitions in the corrugation-weakened LCOs. A phase control may be realized in LCOs by varying the plane corrugation (thus modifying the hole concentration) through an ionic-size change of the neighboring layers on both sides of the cobalt-oxygen layer. In addition, a few experiments are suggested for a check of the present model and picture.