Magnetoresistance Effect in Tunnel Junctions with Perpendicularly Magnetized $D$022-Mn3-\deltaGa Electrode and MgO Barrier

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The tunnel magnetoresistance (TMR) effect with a perpendicularly magnetized $D$022-Mn3-\deltaGa ($\delta = 0.6$) electrode was investigated in epitaxially grown $D$022-Mn3-\deltaGa (30)/Mg ($d_{\text{Mg}}$)/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 $d_{\text{Mg}} = 0.4$ 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 $\Delta_{1}$-bands in Mn3Ga and demonstrated the possibility of a coherent tunneling process existing in the MTJ.
2011-04-25