Crystal electric field of P2-NaxCoO2 for the intermediate spin state of Co3+
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
88
Journal Issue
15
Date Issued
2013
Author(s)
Shu, G. J.
Abstract
The magnetic moment per Co4+ of P2(γ)-type Na xCoO2 in the Curie-Weiss metal regime is revisited and examined under a proposed modification of the octahedral crystal electric field (CEF). The proposed model explains the origin of the existence of the intermediate state S=1 for Co3+ through an exciton-like elementary excitation of the narrow gap between the split eg and t2g groups. The CoO2 layer is proposed to be constructed from the tilted edge-sharing square-planar CoO2 chains with interchain coupling. The square-planar CEF of CoO2 requires covalent bond formation between Co and the four in-plane neighboring oxygens, while the oxygens sitting in the neighboring chains can be viewed as apical oxygens of low effective charge for a CoO6 pseudo-octahedron. The reason why angle-resolved photoemission spectroscopy failed to observe the local-density approximation (LDA) predicted eg′ hole pockets at kz=0 and the reversed order of the t 2g splittings between LDA and CEF calculations can also be resolved using the proposed model. © 2013 American Physical Society.
Type
journal article