Spin state transition and covalent bonding in LaCoO3

TL;DR

This study uses advanced theoretical methods to analyze the spin state transitions and covalent bonding in LaCoO3, revealing complexities beyond simple atomic models and clarifying the origin of local magnetic moments.

Contribution

The paper applies LDA+DMFT to a p-d Hubbard model of LaCoO3, providing new insights into local moments and covalent bonding effects beyond single ion approximations.

Findings

Local moments above 100 K are linked to high-spin Co states.

Single ion models are insufficient to explain covalent bonding effects.

The magnitude of local moments does not directly reflect atomic multiplet states.

Abstract

We use the dynamical mean-field theory to study a p-d Hubbard Hamiltonian for LaCoO3 derived from ab initio calculations in local density approximation (LDA+DMFT scheme). We address the origin of local moments observed above 100 K and discuss their attribution to a particular atomic multiplet in the presence of covalent Co-O bonding. We show that in solids such attribution, based on the single ion picture, is in general not possible. We explain when and how the single ion picture can be generalized to provide a useful approximation in solids. Our results demonstrate that the apparent magnitude of the local moment is not necessarily indicative of the underlying atomic multiplet. We conclude that the local moment behavior in LaCoO3 arises from the high-spin state of Co and explain the precise meaning of this statement.