Spinel oxides: Δ1 spin-filter barrier for a class of magnetic tunnel junctions

The orbital composition of the electrode wave functions and the complex bands within the barrier
band gap are two important factors in deciding the spin-filter effect. This is illustrated in a class of
spinel oxides, including MgAl2O4, ZnAl2O4, SiMg2O4, and SiZn2O4. Through first-principles
calculations of the complex bands and electron transmission along the [001] direction, they are
shown to have the same D1 spin-filter effect as MgO due to the combination of both factors. Due to
better lattice match with typical bcc magnetic electrodes than MgO, these materials provide a
broad spectrum of candidate materials for magnetic tunnel junctions.