Enhanced tunneling magnetoresistance and spin filtering in perovskite magnetic tunnel junctions via oxygen octahedral tilting

Abstract

Oxygen octahedral tilting significantly reduces the symmetry of perovskites and changes the transport properties of perovskite magnetic tunnel junctions (MTJs). We investigated ${\mathrm{SrRuO}}_{3}/{\mathrm{CaTiO}}_{3}/{\mathrm{SrRuO}}_{3}$ MTJs by first-principles simulation and predicted an intriguing coupling between oxygen octahedral tilting and tunneling magnetoresistance. We obtained higher spin polarization at the Fermi level for the ${\mathrm{SrRuO}}_{3}$ electrodes with tilted octahedra, which increases the tunneling magnetoresistance value. Transmission and complex band structure analysis shows that the majority spin tunneling current in the ${\mathrm{CaTiO}}_{3}$ barrier with tilted octahedra is suppressed by wave function symmetry filtering, thus producing a negative spin filtering with an efficiency close to \ensuremath{-}100% and further enhancing the TMR effect. Both phenomena disappear in the junction without oxygen octahedral tilting, hence they have resulted from lattice distortions. The effective control of the tunneling magnetoresistance via oxygen octahedral tilting could act as a way to improve the performances of perovskite spintronic devices.