Half-metallic band structure observed in Co2MnSi-based magnetic tunnel junctions

Magnetic tunnel junctions (MTJs) with stacking structures of Co 2 MnSi/Al–O/CoFe and Co 2 MnSi/Al–O/Co 2 MnSi were fabricated using a magnetron sputtering system. Co 2 MnSi/Al–O/CoFe-MTJ and Co 2 MnSi/Al–O/Co 2 MnSi-MTJ exhibited extremely large tunnelling magnetoresistance ratios of 159% and 570%, respectively, at low temperature, indicating the half-metallicity of Co 2 MnSi. We investigated the bias voltage dependence of tunnelling conductance (d I /d V – V ) for each MTJ in order to clarify the band structure around the Fermi level in Co 2 MnSi. The observed d I /d V – V curves for both MTJs reveal a clear half-metallic energy gap at 350–400 meV for Co 2 MnSi, with an energy separation of just 10 meV between the Fermi energy and the bottom edge of the conduction band.