Co-concentration dependence of half-metallic properties in Co–Mn–Si epitaxial films

Abstract

Co-enriched Co2MnSi epitaxial films, i.e., Co2(1+x)Mn1−xSi1−x (CCMS) were fabricated to investigate the Co-concentration dependence of half-metallicity in a Co–Mn–Si Heusler alloy. The tunnel magnetoresistance ratio in the magnetic tunnel junctions with a CCMS electrode slightly reduces with x from −0.02 to 0.13, then suddenly drops at x=0.20. The half-metallic gap in the G-V curve also disappears when x becomes 0.20. The multiplet structure in x-ray magnetic circular dichroism spectra around Co L-edges, implying half-metallicity of CCMS, also vanishes at x=0.20. These results consistently indicate the half-metallic nature of CCMS is destroyed when the Co atomic concentration is over 57 at. %.