Neutron diffraction andab initiostudies on the fully compensated ferrimagnetic characteristics of Mn₂V_1-CoGa Heusler alloys

Neutron diffraction andab initiostudies were carried out on Mn₂V_1-CoGa (x= 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits highT_Cfully compensated ferrimagnetic characteristics forx= 0.5. A combined analysis of neutron diffraction andab initiocalculations revealed the crystal structure and magnetic configuration which could not be determined from the x-ray diffraction and magnetic measurements. As reported earlier, Rietveld refinement of neutron diffraction data confirmedL2₁structure for Mn₂VGa andX_astructure for Mn₂CoGa. The alloys withx= 0.25 and 0.5 possessL2₁structure with Mn_(C)-Co disorder. As the Co concentration reaches 0.75, a structural transition has been observed from disorderedL2₁to disorderedX_a. Detailedab initiostudies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn₂(V_1-Co)Ga was identified to be different from that of the earlier reported fully compensated ferrimagnet (MnCo)VGa. With the help of neutron diffraction andab initiostudies, it is identified that the disorderedL2₁structure with antiparallel coupling between the ferromagnetically aligned magnetic moments of (Mn_(A)-Mn_(C)) and (V-Co) atom pairs enables the compensation in Mn₂V_1-CoGa.