Electronic and magnetic properties of the kagome systems YBaCo4O7 and YBaCo3MO7 (M=Al, Fe)

TL;DR

This study combines experimental and theoretical XAS to explore the electronic and magnetic properties of kagome cobaltates YBaCo4O7 and YBaCo3FeO7, revealing high spin states and charge configurations in these geometrically frustrated systems.

Contribution

It provides new insights into the local electronic and magnetic structures of these cobaltates, especially regarding spin states and charge distributions in kagome geometries.

Findings

High spin Co2+ and Co3+ states in YBaCo4O7

Exclusive Co2+ and Fe3+ charge states in YBaCo3FeO7

Comparison of spin state stability in tetrahedral vs. octahedral coordination

Abstract

We present a combined experimental and theoretical x-ray absorption spectroscopy (XAS) study of the new class of cobaltates YBaCo4O7 and YBaCo3MO7 (M= Al, Fe). The focus is on the local electronic and magnetic properties of the transition metal ions in these geometrically frustrated kagome compounds. For the mixed valence cobaltate YBaCo4O7, both the Co2+ and Co3+ are found to be in the high spin state. The stability of these high spin states in tetrahedral coordination is compared with those in the more studied case of octahedral coordination. For the new compound YBaCo3FeO7, we find exclusively Co2+ and Fe3+ as charge states.