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

Abstract

Magnetic tunnel junctions (MTJs) with stacking structures of Co2MnSi/Al–O/CoFe and Co2MnSi/Al–O/Co2MnSi were fabricated using a magnetron sputtering system. Co2MnSi/Al–O/CoFe-MTJ and Co2MnSi/Al–O/Co2MnSi-MTJ exhibited extremely large tunnelling magnetoresistance ratios of 159% and 570%, respectively, at low temperature, indicating the half-metallicity of Co2MnSi. We investigated the bias voltage dependence of tunnelling conductance (dI/dV–V) for each MTJ in order to clarify the band structure around the Fermi level in Co2MnSi. The observed dI/dV–V curves for both MTJs reveal a clear half-metallic energy gap at 350–400 meV for Co2MnSi, with an energy separation of just 10 meV between the Fermi energy and the bottom edge of the conduction band.