Electronic structure of normal and inverse spinel ferrites from first principles

TL;DR

This study uses first-principles calculations to analyze the electronic and magnetic properties of various spinel ferrites, revealing differences between normal and inverse structures and highlighting orbital moments in specific compounds.

Contribution

It provides a detailed first-principles analysis of the electronic structure and magnetic properties of spinel ferrites, clarifying valence states and structural effects.

Findings

All compounds are insulating with smaller gaps in normal spinel structure.

Spin magnetic moments increase from inverse to normal spinel structures.

Substantial orbital moments are found in NiFe₂O₄ and CoFe₂O₄.

Abstract

We apply the self-interaction corrected local spin density %(SIC-LSD) approximation to study the electronic structure and magnetic properties of the spinel ferrites MnFe$_{2}$O$_{4}$, Fe$_{3}$O$_{4}$, CoFe$_{2}$O$_{4}$, and NiFe$_{2}$O$_{4}$. We concentrate on establishing the nominal valence of the transition metal elements and the ground state structure, based on the study of various valence scenarios for both the inverse and normal spinel structures for all the systems. For both structures we find all the studied compounds to be insulating, but with smaller gaps in the normal spinel scenario. On the contrary, the calculated spin magnetic moments and the exchange splitting of the conduction bands are seen to increase dramatically when moving from the inverse spinel structure to the normal spinel kind. We find substantial orbital moments for NiFe$_{2}$O$_{4}$ and CoFe$_{2}$O$_{4}$.