Pressure-induced half-metallic gap transformation in Co_2MnSi observed by tunneling conductance spectroscopy

摘要

Applied hydrostatic pressure dependence of tunneling magnetoresistance (TMR) properties was investigated in magnetic tunnel junctions using the half-metallic Heusler alloy Co_2MnSi (CMS). The half-metallic electronic structure in CMS was observed by measuring tunneling-conductance spectroscopy under different applied pressure. The effect of tetragonal distortion in CMS on the electronic structure was also calculated on th basis of the first-principle density-functional method. The TMR ratio showed no remarkable variation with increasing pressure from ambient to 1.5 GPa. It was clearly found that the valence-band edge of the half-metallic gap moved toward the Fermi level with increasing pressure up to 1.8 GPa. These experimental results showed good qualitative agreement with the theoretical calculation of density of states of CMS at high pressure.