Orbital occupation and magnetic moments of tetrahedrally coordinated iron in CaBaFe4O7

TL;DR

This study investigates the electronic structure and magnetic properties of CaBaFe4O7, revealing a Jahn-Teller active Fe2+ ion with an orbital moment contributing to magnetic anisotropy, using spectroscopy and theoretical calculations.

Contribution

It provides the first detailed characterization of the local electronic structure and magnetic moments of tetrahedral Fe2+ in CaBaFe4O7, combining experimental and theoretical approaches.

Findings

Fe2+ in CaBaFe4O7 is Jahn-Teller active with a high-spin configuration.

An orbital moment of about L_z=0.36 was deduced, explaining magnetic anisotropy.

The study offers insights into charge, orbital, and spin physics in transition metal oxides.

Abstract

CaBaFe4O7 is a mixed-valent transition metal oxide having both Fe2+ and Fe3+ ions in tetrahedral coordination. Here we characterize its magnetic properties by magnetization measurements and investigate its local electronic structure using soft x-ray absorption spectroscopy at the Fe L2,3 edges, in combination with multiplet cluster and spin-resolved band structure calculations. We found that the Fe2+ ion in the unusual tetrahedral coordination is Jahn-Teller active with the high-spin e^2 (up) t2^3 (up) e^1 (down) configuration having a x^2-y^2-like electron for the minority spin. We deduce that there is an appreciable orbital moment of about L_z=0.36 caused by multiplet interactions, thereby explaining the observed magnetic anisotropy. CaBaFe4O7, a member of the '114' oxide family, offers new opportunities to explore charge, orbital and spin physics in transition metal oxides.