Effect of Co substitution for Mn on spin polarization and magnetic properties of ferrimagnetic Mn2VAl

Bulk (Mn1-xCox)2VAl (x = 0, 0.25, 0.50) alloys in highly ordered L21 structure with a very small amount of B2 disorder have been prepared and their magnetic properties have been measured. The value of saturation magnetizations of the alloys with x = 0, 0.25 and 0.50 are 1.88 μB, 0.84 μB and 0.07 μB, respectively, being consistent with 2.00 μB, 1.00 μB and 0 μB, respectively, predicted by the Slater–Pauling rule. This indicates that the stoichiometric MnCoVAl alloy is a fully compensated ferrimagnet (FCF). Spin polarization measurements using point contact Andreev reflection technique showed that the quaternary alloys exhibited higher intrinsic spin polarization than the parent ternary composition. The spin polarization of 0.60 deduced for the MnCoVAl alloy suggests that spin-polarized current can be extracted from FCF. Curie temperature (TC) and the effective anisotropy constant of (Mn1-xCox)2VAl alloys decrease with increase in Co content.