Magnetic properties and spin polarization of Co2Mn(SixSn1−x) alloys containing two L21 phases

Bulk Co2Mn(SixSn1−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 L21 phases, Co2MnSi and Co2MnSn 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 Co2Mn(Si0.5Sn0.5) alloy. These studies show that isovalent substitution for Sn with Si in Co2MnSn results in enhanced intrinsic spin polarization in spite of the phase separation.

► Co2Mn(SixSn1−x) alloys with two L21 phases have been synthesized.
► Magnetization of the quaternary alloys obeys the Slater–Pauling rule despite the phase separation.
► Intrinsic spin polarization of the quaternary alloys is higher than that of the parent ternary alloys.
► Intrinsic spin polarization of a Heusler alloy with isovalent substitution for the sp element is reported for the first time.