Magnetoresistance Effect in Tunnel Junctions with Perpendicularly Magnetized D022-Mn3-δGa Electrode and MgO Barrier

The tunnel magnetoresistance (TMR) effect with a perpendicularly magnetized D022-Mn3-δGa (δ= 0.6) electrode was investigated in epitaxially grown D022-Mn3-δGa (30)/Mg (dMg)/MgO (2)/CoFe (2.5) (nm) magnetic tunnel junctions (MTJs). The maximum TMR ratio of 9.8% (22.1%) was achieved at 300 K (10 K) with dMg = 0.4 nm. The bias voltage dependence of differential conductance spectra suggests the existence of a coherent tunneling process in the MTJs. First principles calculations of band dispersion relations and tunneling transmittance in a Mn3Ga/MgO/Mn3Ga structure were also performed. The results revealed the existence of Δ1-bands in Mn3Ga and demonstrated the possibility of a coherent tunneling process existing in the MTJ.