Spin polarization of Fe-rich ferromagnetic compounds in Ru2−xFexCrSi Heusler alloys

We report spin polarization P of Ru2−xFexCrSi Heusler alloys by the Andreev reflection technique. Ru2−xFexCrSi with L21-type structure and saturation magnetic moment of 2μB per formula unit is theoretically predicted to be half-metals in the wide range of the composition x. We had clarified that the experimental results of saturation magnetic moment in Fe-rich compounds had coincided with the theoretical prediction. Therefore, we have measured the differential conductance of Ru2−xFexCrSi/Pb planar-type junctions. The P value of Ru2−xFexCrSi was determined by fitting the differential conductance with the modified Blonder–Tinkham–Klapwijk theory. We have found that the behavior of P for Ru2−xFexCrSi was independent of the composition x in the Fe-rich region; P=0.53 for both of x=1.5 and 1.7. The spin polarization is the similar value to Co-based Heusler alloys.