Magnetization reversal of giant perpendicular magnetic anisotropy at the magnetic-phase transition in FeRh films on MgO

Based on first-principles calculations, we demonstrate that substitutions of transition metals Ru and Ir, neighboring and same group elements in the periodic table, for the Rh site in the vicinity of surface can induce a substantially large perpendicular magnetic anisotropy (PMA), up to an order of magnitude of 20 erg/cm², in FeRh films on MgO. The main driving mechanism for this huge PMA is the interplay between the dxy and d_x²-y² orbital states of the substitutional $4d$ and $5d$ transition metal atoms with large spin-orbit coupling. Further investigations demonstrate that magnetization direction of PMA undergoes a transition into an in-plane magnetization at the antiferromagnet → ferromagnet phase transition, which provides a viable route for achieving large and switchable PMA associated with the magnetic-phase transition in antiferromagnet spintronics.