Magnetization and Spin Polarization of Heusler Alloys Co₂TiSn and Co₂ TiGa_0.5Sn_0.5

The substitution effect on half-metallicity for Co-based Heusler alloys Co₂TiGa_1-x Sn_x was investigated by experimental measurements and first-principles band calculations. The synthesized alloys crystalized in the ordered L2₁ crystal structure. The spontaneous magnetization obeyed the Slater-Pauling rule, indicating the possibility that Co₂TiSn and Co₂TiGa_0.5Sn_0.5 are half-metals. The first-principles band calculations revealed that Co₂TiSn is half-metal and Co₂TiGa_0.5Sn_0.5 is nearly half-metal. The spin polarization P was determined by the Andreev reflection technique. The intrinsic P values were 58.9% for Co₂TiSn and 58.2% for Co₂TiGa_0.5 Sn_0.5, respectively. The P values of Co₂TiGa_1-xSn_x were relatively higher than other Co-based Heusler alloys. Thus, Co-based Heusler alloys Co₂TiGa_1-xSn_x are possible candidates for half-metallic electrode materials in spintronic devices.