First Principle Study of Magnetism and Magneto-structural Coupling in Gallium Ferrite

TL;DR

This study uses first-principles calculations to explore the magnetic properties, site disorder, and magneto-structural coupling in gallium ferrite, revealing how site disorder influences ferrimagnetism and structural distortions.

Contribution

It provides a detailed first-principles analysis of magnetism and magneto-structural coupling in GFO, highlighting the role of site disorder in its ferrimagnetic behavior.

Findings

Magnetic moments align with experimental data.

Site disorder between Fe2 and Ga2 is energetically favored.

Magneto-structural coupling is evidenced by structural distortions linked to spin configurations.

Abstract

We report a first-principles study of the magnetic properties, site disorder and magneto-structural coupling in multiferroic gallium ferrite (GFO) using local spin density approximation (LSDA+U) of density functional theory. The calculations of the ground state A-type antiferromagnetic structure predict magnetic moments consistent with the experiments whilst consideration of spin-orbit coupling yields a net orbital moment of ~ 0.025 Bohr magneton/Fe site also in good accordance with the experiments. We find that though site disorder is not spontaneous in the ground state, interchange between Fe2 and Ga2 sites is most favored in the disordered state. The results show that ferrimagnetism in GFO is due to Ga-Fe site disordering such that Fe spins at Ga1 and Ga2 sites are antiferromagnetically aligned while maintaining ferromagnetic coupling between Fe spins at Ga1 and Fe1 sites as well as between Fe spins at Ga2 and Fe2 sites. The effect of spin configuration on the structural distortion clearly indicates presence of magneto-structural coupling in GFO.