Magnetic and transport properties of Mn 3-xGa/MgO/Mn 3-xGa magnetic tunnel junctions: A first-principles study

Abstract

Magnetic and transport properties of Mn 3-xGa/MgO/Mn 3-xGa (0≤x≤1) magnetic tunnel junctions are studied using first-principles approach based on density functional theory and non-equilibrium Green's function. Perpendicular magnetization, of which the magnetic anisotropy energy reaches more than 1 meV/unit-cell, is confirmed to be energetically favoured by both Mn 2Ga and Mn 3Ga thin films. Furthermore, despite high spin-polarization at the Fermi energy for both these compounds as reported, our transport calculation shows considerable disparity in the transmission behaviour between Mn 2Ga/MgO/Mn 2Ga(001) and Mn 3Ga/MgO/Mn 3Ga(001) magnetic tunnel junctions: huge optimistic tunneling magnetoresistance ratio of 10 3% for the former, and nevertheless, no tunneling magnetoresistance effect absolutely for the latter. This phenomenon is attributed to the symmetry selective filtering effect of the MgO spacer. On this premise, Mn 3-xGa compounds with low Mn concentration are predicted to be promising candidate materials to serve as the electrodes of spin-transfer torque devices in the next-generation data storage technique. © 2012 American Institute of Physics.