Tuning structural and magnetic properties by vanadium substitution in Fe₃Ge

The structural and magnetic properties of Fe_3-xV_xGe intermetallic alloy series (0<x≤1) have been investigated. The samples were prepared by arc-melting under argon atmosphere. After annealing, alloys with 0.375≤x≤0.625 are found to crystallize in the cubic Heusler structure, while alloys with 0<x≤0.25 crystallize in the hexagonal DO_19, which is the high temperature phase of parent Fe₃Ge. Optical microscopy, EDX, and XRD reveal uniform granular microstructures for x≤0.75.The calculated lattice parameter increases linearly with increasing x, while the magnetic moment at 5K decreases linearly for cubic alloys, deviating only about 7% from the Slater-Pauling values, which indicates possible half-metallic behavior. The hexagonal samples have markedly higher moments. The saturation magnetizing field is found to decrease with the increase of x making the system softer at higher V concentrations.The martensitic phase transformation in all stable cubic phases is confirmed by DSC which is being reported for the first time for this system. Vanadium is found to play a crucial role in stabilizing the cubic structure and shifting the martensitic transformation temperature to higher values from that of parent Fe₃Ge.