Perpendicular magnetic anisotropy induced by antiferromagnetic Mn-Pd alloy films: Dual effects of exchange and spin-orbit coupling

Abstract

Ferromagnetic (FM) films with perpendicular magnetic anisotropy (PMA) are crucial building blocks of state-of-the-art perpendicular magnetic devices. This study investigated the effects of triggering PMA in FM thin films by applying ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$-based antiferromagnetic (AFM) thin films with strong AFM exchange coupling from Mn and high spin-orbit coupling from Pd atoms. Our results reveal that ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$ films can trigger PMA in Co/Ni films with weak in-plane magnetic anisotropy at room temperature through either ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$-facilitated interfacial perpendicular crystalline anisotropy (spin-orbit coupling, $x \ensuremath{\ge}10%$) or incorporation of them with antiferromagnet-induced exchange coupling ($x \ensuremath{\le}10%$). In Co/Fe films with strong in-plane magnetic anisotropy, Mn-rich ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$ films ($x \ensuremath{\le}10%$) can induce stable PMA at low temperatures through concurrently enhanced spin-orbit coupling and antiferromagnet-induced exchange coupling across the AFM--FM interface. Our research clarifies the dual effects of exchange and spin-orbit coupling in ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$ films, which trigger the PMA of adjacent FM films. This indicates that ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Pd}}_{x}$ films are promising candidates for achieving controllable PMA.