Near total magnetic moment compensation with high Curie temperature in Mn2V0.5Co0.5Z (Z = Ga,Al) Heusler alloys

Abstract

Mn2V1−xCoxZ (Z = Ga,Al and x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys have been synthesized to investigate the effect of Co substitution at the V site on the magnetic moment and Curie temperature of half-metallic ferrimagnets Mn2VGa and Mn2VAl. Near total magnetic moment compensation was achieved with high Curie temperature for x = 0.5 composition. The Co substituted alloys show a non linear decrease in lattice parameter without altering the crystal structure of the parent alloys. The end members Mn2VGa and Mn2CoGa have the saturation magnetization of 1.80 µB/f.u. and 2.05 µB/f.u. respectively whereas for the Mn2V0.5Co0.5Ga alloy, a near total magnetic moment compensation (0.10 µB/f.u.) was observed due to the ferrimagnetic coupling of Mn with parallelly aligned V and Co. The Co substituted Mn2VAl has also shown a similar trend with compensated magnetic moment value of 0.06 µB/f.u. for x = 0.5. The Curie temperatures of the alloys including the x = 0.5 composition are well above the room temperature (more than 650 K) which is in sharp contrast to the earlier reported values of 171 K for the (MnCo)VGa and 105 K for the (MnCo)VAl (substitution at the Mn site). The observed TC values are highest among the Mn2V based fully compensated ferrimagnets. The magnetic moment compensation without significant reduction in TC indicates that the V site substitution of Co does not weaken the magnetic interaction in Mn2VZ (Z = Ga,Al) alloys which is contrary to the earlier experimental reports on Mn site substitution.