Symmetry-driven large tunneling magnetoresistance in SrRuO3 magnetic tunnel junctions with perpendicular magnetic anisotropy

Magnetic tunnel junctions (MTJs) that are comprised of epitaxially grown complex oxides offer a versatile platform to control the symmetry of tunneling states and tailor magnetic anisotropy useful for practical applications. This work employs thin films of ${\mathrm{SrTiO}}_3$ as an insulating barrier deposited between two ferromagnetic ${\mathrm{SrRuO}}_3$ electrodes to form fully epitaxial MTJs and demonstrate these functionalities. Transport measurements demonstrate large tunneling magnetoresistance (TMR), significantly exceeding previously found values of TMR in MTJs based on ${\mathrm{SrRuO}}_3$ electrodes. These results are explained by perpendicular magnetic anisotropy of ${\mathrm{SrRuO}}_3$ and matching (mismatching) between symmetry and spin across the ${\mathrm{SrTiO}}_3/{\mathrm{SrRuO}}_3$ (001) interface for the parallel (antiparallel) MTJ magnetization state, supported by density functional (DFT) calculations. The angular variation of TMR indicates that the ${\mathrm{SrRuO}}_3$ electrodes contain multiple magnetic domains, allowing the devices to exhibit at least three stable resistance states.