Magnetic properties and spin polarization of Co ₂Mn(Si _xSn _1-x) alloys containing two L2 ₁ phases

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.