Neutron diffraction and ab initio studies on the fully compensated ferrimagnetic characteristics of Mn 2 V 1- x Co x Ga Heusler alloys.

Neutron diffraction and ab initio studies were carried out on Mn 2 V 1- x Co x Ga ( x = 0, 0.25, 0.5, 0.75, 1) Heusler alloys which exhibits high T C fully compensated ferrimagnetic characteristics for x = 0.5. A combined analysis of neutron diffraction and ab initio calculations 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 confirmed L 2 1 structure for Mn 2 VGa and X a structure for Mn 2 CoGa. The alloys with x = 0.25 and 0.5 possess L 2 1 structure with Mn (C) -Co disorder. As the Co concentration reaches 0.75, a structural transition has been observed from disordered L 2 1 to disordered X a . Detailed ab initio studies also confirmed this structural transition. The reason for the magnetic moment compensation in Mn 2 (V 1- x Co x )Ga was identified to be different from that of the earlier reported fully compensated ferrimagnet (MnCo)VGa. With the help of neutron diffraction and ab initio studies, it is identified that the disordered L 2 1 structure with antiparallel coupling between the ferromagnetically aligned magnetic moments of (Mn (A) -Mn (C) ) and (V-Co) atom pairs enables the compensation in Mn 2 V 1- x Co x Ga.