Perpendicularly magnetized synthetic antiferromagnetic Mn_xGa/Co₂FeAl bilayers on MgAl₂O₄ substrate

Magnetic tunneling junctions (MTJs) with MgAl₂O₄ (MAO) barrier exhibit large tunnel magnetoresistance, comparable to that of MgO barrier. In this study, we grow synthetic antiferromagnetic Mn_xGa/Co₂FeAl (CFA) bilayers on MAO (001) substrates without any buffer layer, where the Mn_xGa layer includes D0₂₂-Mn₃Ga and L1₀-MnGa phases. Our results indicate that the CFA forms antiferromagnetic coupling with both D0₂₂-Mn₃Ga and L1₀-MnGa. Moreover, we observe the perpendicular magnetic anisotropy (PMA) in both L1₀-MnGa/CFA and D0₂₂-Mn₃Ga/CFA bilayers, which is induced by tetragonal Mn_xGa and interfacial magnetic coupling. Particularly, the L1₀-MnGa(10 nm)/CFA(1.5 nm) bilayer exhibits a perpendicular anisotropy field of 72.08 kOe and a perpendicular anisotropy energy of 7.57 × 10⁶ erg/cm³. Similar PMA is also observed in L1₀-MnGa/Co₂MnAl and L1₀-MnGa/Co₂FeGa bilayers on MAO substrates. These results provide a foundation for the development of high-performance perpendicular MTJs with MAO barrier.