Magnetic Compton scattering study of Ni_(2+x)Mn_(1-x)Ga ferromagnetic shape-memory alloys

摘要

In this paper, we report the spin-polarized momentum densities of Ni_(2+x)Mn_(1-x)Ga (x=0.03, 0.26, and 0.35) Heusler alloys at various temperatures and magnetic fields using magnetic Compton scattering technique. Magnetization studies are also performed for comparison. It is seen that the variation of magnetic effect (ratio of magnetic to charge intensities) is consistent with the martensitic transition, as shown by the differential scanning calorimetry data. The magnetic Compton profiles have been analyzed mainly in terms of the contributions from the 3d electrons of Mn to determine their role in the formation of total spin moment. The full potential linearized augmented plane-wave method has been used to calculate the spin-polarized energy bands and the spin moments of Ni_2MnGa and Ni_(2.25)Mn_(0.75)Ga. Ni_2MnGa exhibits half metallicity along certain high-symmetry directions of the Brillouin zone. For Ni_2MnGa, the total and Mn local moments obtained from Compton scattering are in excellent agreement with theory.