RESUMO
Neutron diffraction andab initiostudies were carried out on Mn2V1-xCoxGa (x= 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits highTCfully 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 andXastructure 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 disorderedXa. Detailedab initiostudies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn2(V1-xCox)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 Mn2V1-xCoxGa.
