Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6

TL;DR

This study uses density functional theory to analyze the electronic structure and magnetic properties of Ca3Co2O6, revealing complex spin states, hybridization effects, and intrachain ferromagnetic coupling in this one-dimensional magnetic compound.

Contribution

It provides a detailed theoretical understanding of the electronic and magnetic structure of Ca3Co2O6, highlighting the role of spin state alternation and hybridization in its magnetic behavior.

Findings

Alternation of low- and high-spin Co states along chains.

Strong hybridization between Co d and O p states.

Intrachain ferromagnetic exchange via d_{3z^2-r^2} orbitals.

Abstract

The results of electronic structure calculations for the one-dimensional magnetic chain compound Ca3Co2O6 are presented. The calculations are based on density functional theory and the local density approximation and used the augmented spherical wave (ASW) method. Our results allow for deeper understanding of recent experimental findings. In particular, alternation of Co 3d low- and high-spin states along the characteristic chains is related to differences in the oxygen coordination at the inequivalent cobalt sites. Strong hybridization of the d states with the O 2p states lays ground for polarization of the latter and the formation of extended localized magnetic moments centered at the high-spin sites. In contrast, strong metal-metal overlap along the chains gives rise to intrachain ferromagnetic exchange coupling of the extended moments via the d_{3z^2-r^2} orbitals of the low-spin cobalt atoms.