Tunnel Magnetoresistance of Ferromagnetic Antiperovskite MnGaN/MgO/CoFeB Perpendicular Magnetic Tunnel Junctions

We report on the tunnel magnetoresistance (TMR) effect of perpendicular magnetic tunnel junctions (p-MTJs) composed of a ferromagnetic antiperovskite MnGaN film with perpendicular magnetic anisotropy. The p-MTJ multilayer stack with MnGaN/Mg/MgO/Fe/CoFeB was used to control the MgO interface conditions by the Mg and Fe insertion layers. The Mg insertion under the MgO barrier enhanced the perpendicular anisotropy of the top Fe/CoFeB layers with post-annealing process, and thus nearly perfect perpendicular magnetization was realized. A perpendicular TMR ratio up to 3.7% $\sim 3.8$ % was obtained at room temperature. The obtained low TMR ratio is mainly attributed to the imperfect MgO barrier, which includes many lattice-misfit dislocations at the MnGaN/MgO interface due to the large lattice mismatch of 8%. This paper suggests that improving the interface state and reducing the lattice mismatch will be required to observe a higher perpendicular TMR ratio using an MnGaN electrode.