Electronic structure, Born effective charges and spontaneous polarization in magnetoelectricgallium ferrite

Abstract

We present a theoretical study of the structure–property correlation ingallium ferrite, based on first-principles calculations followed by a subsequentcomparison with experiments. The local spin density approximation (LSDA + U) of the density functional theory has been used to calculate the ground statestructure, electronic band structure, density of states and Born effective charges.The calculations reveal that the ground state structure is orthorhombicPc 21n having A-type antiferromagnetic spin configuration, with lattice parameters matching wellwith those obtained experimentally. Plots of the partial density of states of constituent ionsexhibit noticeable hybridization of Fe 3d, Ga 4s, Ga 4p and O 2p states. However,the calculated charge density and electron localization function show a largelyionic character of the Ga/Fe–O bonds which is also supported by a lack of anysignificant anomaly in the calculated Born effective charges with respect to thecorresponding nominal ionic charges. The calculations show a spontaneous polarization of ∼ 59 µC cm − 2 alongthe b-axis which is largely due to asymmetrically placed Ga1, Fe1, O1, O2 and O6 ions.