Electronic structure near the Fe3O4/MgO(001) interface and near structural defects in magnetite

Magnetite (Fe₃O₄) is particularly interesting at high temperature where it shows a half-metallic behavior and possesses the high Curie temperature of 858 K. With these remarkable characteristics, it should be an ideal electrode material for magnetic tunnel junctions (MTJs), ensuring a quasi infinite magnetoresistance ratio. Unfortunately, the tunnel magnetoresistance measured with these junctions is rather small. In order to try to explain these disappointing experimental results, I will present DFT results (obtained with the LSDA, LSDA+U and PBE0 approximations) on the electronic structure of the high temperature cubic phase of magnetite. I show how the electron states and spin magnetic moments are modified in the vicinity of structural defects like point defects (oxygen or iron vacancies, excess of Fe atoms in atomic sites which should be empty, atomic site inversion) or bidimensional defects (antiphase boundaries). I will also describe the electronic structure at the Fe₃O₄/MgO(001) interface, emphazing on the localized interface states which could play a role in tunnel junctions.