Voltage controlled magnetic anisotropy at iron/spinel oxide interfaces

Abstract

The ability to use an applied voltage to effectively manipulate perpendicular magnetic anisotropy is critical for high density, robust magnetic random access memory devices. Using first principle simulations, we examine voltage control of perpendicular magnetic anisotropy at the interface between Fe and several different spinel oxides (MgAl2O4, MgGa2O4, and ZnAl2O4). These spinel oxides have an excellent lattice match with Fe and there is good alignment of spinel O atoms with Fe atoms at the interface. We find that all of these Fe|spinel oxide interfaces have high perpendicular magnetic anisotropy ranging from 1.87 to 1.89mJ/m2. The two Fe layers closest to the oxide interface provide significant contributions to the magnetic anisotropy. Calculations for Cu|Fe|spinel slabs under applied fields indicate VCMA coefficients in the range of (25–30 fJ V m) which are comparable to that found for Fe|MgO. Given the excellent lattice match with (001) bcc Fe for all of these spinel oxides and the demonstrated high TMR for the case of Fe|MgAl2O4, our results indicate that members of this spinel oxide family are promising candidates for tunneling barriers in future voltage controlled MRAM devices.