Valence, spin, and orbital state of the Co ions in the one-dimensional Ca3Co2O6: an x-ray absorption and magnetic circular dichroism study

TL;DR

This study uses x-ray absorption and magnetic circular dichroism to determine the valence, spin, and orbital states of Co ions in Ca3Co2O6, revealing a low-spin state at octahedral sites and a high-spin state with large orbital moment at trigonal sites.

Contribution

It provides detailed insights into the electronic and magnetic states of Co ions in Ca3Co2O6, highlighting the large orbital moment and anisotropy due to trigonal crystal field effects.

Findings

Co ions are in a 3+ valence state at both sites

Octahedral Co is in a low-spin state

Trigonal Co has a high-spin state with a large orbital moment

Abstract

We have investigated the valence, spin, and orbital state of the Co ions in the one-dimensional cobaltate Ca3Co2O6 using x-ray absorption and x-ray magnetic circular dichroism at the Co-L2,3 edges. The Co ions at both the octahedral Co_oct and trigonal Co_trig sites are found to be in a 3+ state. From the analysis of the dichroism we established a low-spin state for the Co_oct and a high-spin state with an anomalously large orbital moment of 1.7 muB at the Co3+ trig ions. This large orbital moment along the c-axis chain and the unusually large magnetocrystalline anisotropy can be traced back to the double occupancy of the d2 orbital in trigonal crystal field.