Bulk Co 2Mn(Si xSn 1-x) (0 < x < 1) alloys have been prepared and their crystal structure, magnetization and spin polarization have been measured. X-ray diffraction pattern and scanning electron micrograph revealed the alloy phase separate into two L2 1 phases, Co 2MnSi and Co 2MnSn for x ≥ 0.25. The saturation magnetization values corresponded to the value predicted by the Slater-Pauling (S-P) rule. Spin polarization measurements using point contact Andreev reflection (PCAR) technique showed that the quaternary alloys exhibited higher intrinsic spin polarization than the parent ternary compositions. The highest spin polarization of 0.67 ± 0.01 was obtained for the Co 2Mn(Si 0.5Sn 0.5) alloy. These studies show that isovalent substitution for Sn with Si in Co 2MnSn results in enhanced intrinsic spin polarization in spite of the phase separation.
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