Spin Polarization Measurements of Heusler Alloy ${\hbox {Ru}}_{0.2}{\hbox {Fe}}_{1.8}{\hbox {CrSi}}$ by Andreev Reflection Technique

We report spin polarization P of Fe-rich Heusler alloy Ru_0.2Fe_1.8CrSi, which was determined by the Andreev reflection technique. Heusler alloy Ru_2-xFe_xCrSi was predicted to be half-metal by the first-principle band calculations. Fe-rich Ru_0.2Fe_1.8CrSi compounds are ferromagnetic and the saturation magnetization M₀ almost coincides with that expected from the Slater-Pauling rule. Two theoretical approaches in the determination of spin polarization by Andreev reflection are discussed and compared from an experimental perspective. The spin polarization more than P=0.60 is obtained for Ru_0.2Fe_1.8CrSi specimens and it is highest value in all Ru_2-xFe_xCrSi compounds. The difference in values of spin polarization as determined by two models is less than 0.02.