How does the spin-state of Co ions affect the insulator-metal transition in Bi₂A₂Co₂O₈ (A = Ca, Sr, Ba)?

ABSTRACT: The misfit layered Bi₂A₂Co₂O₈ (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A's ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co³⁺ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO₂ plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi₂Ca₂Co₂O₈ and Bi₂Sr<

SUBMITTER: Huang X 

PROVIDER: S-EPMC5128795 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature