Theoretical study on tunneling magnetoresistance of magnetic tunnel tunctions with D0₂₂-Mn₃Z (Z = Ga, Ge)

We investigated spin dependent transport properties of magnetic tunnel junctions (MTJs) with D0₂₂-Mn₃ Ga or Mn₃ Ge using the first-principles electronic and ballistic-transport calculations. We found that tunneling magntoresistance (TMR) ratios of Mn₃ Ga/MgO(1 nm)/Mn₃ Ga(001) MTJs depend strongly on the interfacial structures, which are about 600% for MnMn termination and 40% for MnGa termination. The relatively small TMR ratio of MnGa termination can be attributed to a presence of the Δ₁ state around the Fermi level in both spin channels. On the other hand, we obtained over 4000% TMR ratios both for MnMn and MnGe terminations of Mn₃ Ge-based MTJs due to the half-metallic electronic structure on the Δ₁ state. We concluded that D0 ₂₂-Mn₃ Ge is a promising material providing large TMR effects as well as strong perpendicular magnetic anisotropy.