Inverse tunnel magnetoresistance in all-perovskite junctions of La 0.7 Sr 0.3 MnO 3 / SrTiO 3 / SrRuO 3

All epitaxial oxide magnetic tunnel junctions, ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}/{\mathrm{SrTiO}}_{3}/{\mathrm{SrRuO}}_{3}$ trilayer films, composed of ferromagnetic and metallic electrodes were fabricated on STO(001) substrates. Inverse tunnel magnetoresistance (TMR), i.e., higher and lower junction resistance levels in parallel and anti-parallel magnetization configurations, respectively, was observed, indicating the negative spin polarization of ${\mathrm{SrRuO}}_{3}$ in contrast to the positive one of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}.$ The TMR action persists up to ${T}_{\mathrm{C}}$ of the ${\mathrm{SrRuO}}_{3}$ layer due to the robust spin polarization at the ${\mathrm{SrTiO}}_{3}/{\mathrm{SrRuO}}_{3}$ interface.