Ferromagnetism with Strong Perpendicular Magnetic Anisotropy in Epitaxial SrMn0.3Ir0.7O3 Perovskite Films

Abstract

Strong Coulomb repulsion and spin-orbit coupling are known to give rise to exotic physical phenomena in transition metal oxides. Here, we report magnetic characteristics of a ${\mathrm{Sr}\mathrm{Mn}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_{3}$ perovskite thin film, having both 3d and 5d elements on the $B$ sites, with a strong perpendicular magnetic anisotropy (PMA), which is rare in perovskite oxide thin films. The ${\mathrm{Sr}\mathrm{Mn}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_{3}$ films have been epitaxially deposited on (001)-oriented ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_{3}$ single-crystal substrates by pulsed-laser deposition, exhibiting a para-to-ferromagnetic transition at about 110 K. The average valence of $\mathrm{Mn}$ and $\mathrm{Ir}$ cations are estimated as +3.61 and +4.17, respectively, by x-ray photoelectron spectroscopy. X-ray absorption spectroscopy reveals that $\mathrm{Mn}$ ${e}_{g}$ electrons occupy preferentially the ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbital, which produces the observed PMA in the framework of spin-orbital coupling. The ${\mathrm{Sr}\mathrm{Mn}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_{3}$ thin film shows a large effective anisotropy constant of about 1.2 \ifmmode\times\else\texttimes\fi{} ${10}^{6}$ erg ${\mathrm{cm}}^{\ensuremath{-}3}$ at 10 K, which is found to decrease with decreasing tetragonality c/a of the film. First-principles calculations reveal that $\mathrm{Mn}$ and $\mathrm{Ir}$ cations provide opposite magnetizations in ${\mathrm{Sr}\mathrm{Mn}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_{3}$ and the $\mathrm{Mn}$ ${e}_{g}$ orbital polarization comes from both lattice distortion and oxygen octahedron rotation. The ${\mathrm{Sr}\mathrm{Mn}}_{0.3}{\mathrm{Ir}}_{0.7}{\mathrm{O}}_{3}$ thin film with strong PMA may have applications in future low-power-consumption oxide spintronic devices.