We have investigated the structure and the spin polarization of Co2 MnAl, Co2 MnSn, and Co2 Mn Al0.5 Sn0.5 alloys. The structures of the Co2 MnAl and Co2 MnSn alloys that were annealed for four days at 450 °C were B2 and L 21, respectively. Co2 Mn Al0.5 Sn0.5 had a dendrite microstructure that was formed by the phase separation into Al-enriched B2 and Sn-enriched L 21 phases during solidification. The saturation magnetization values of Co2 MnAl, Co2 Mn Al0.5 Sn0.5, and Co2 MnSn were 3.66 μB, 4.3 μB, and 4.9 μB, respectively, which are slightly lower than the theoretical values of 4 μB, 4.5 μB, and 5 μB due to the low degree of L 21 ordering. The spin polarization P measured by the point contact Andreev reflection technique were 0.56 for B2- Co2 MnAl, 0.6 for L 21 - Co2 MnSn, and interestingly, a higher value of 0.63 for the two phase Co2 Mn Al0.5 Sn0.5 alloy.
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