Interfacial resonant tunneling induced by folded bands and providing highly spin-polarized current in spinel-oxide barrier junctions

Abstract

In spintronics, simultaneous realization of high tunneling magnetoresistance and low resistivity in magnetic tunnel junctions (MTJs) is challenging because insulating layers with higher barrier heights generally generate highly spin-polarized currents but increase resistivity. We overcome this trade-off relationship using Brillouin-zone-folded bands at the interfaces in the Fe/spinel ${\mathrm{MgGa}}_{2}{\mathrm{O}}_{4}/\mathrm{Fe}\phantom{\rule{0.16em}{0ex}}\mathrm{MTJ}$. Interfacial resonant states that enhance conductance are formed by folded bands, with Fe--O hybridization playing a key role in the resonant effect intensity at the Fermi level. The electronegativity of cation Ga in spinel oxide ${\mathrm{MgGa}}_{2}{\mathrm{O}}_{4}$ is found to be a crucial physical quantity to control an intensity of the interfacial-resonant effect from the comparative analysis with the ${\mathrm{MgAl}}_{2}{\mathrm{O}}_{4}$-based MTJ.