Magnetic Compton scattering study of Ni2+xMn1−xGa ferromagnetic shape-memory alloys

In this paper, we report the spin-polarized momentum densities of ${\mathrm{Ni}}_{2+x}{\mathrm{Mn}}_{1\ensuremath{-}x}\mathrm{Ga}$ ($x=0.03$, 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 ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{G}\mathrm{a}$ and ${\mathrm{Ni}}_{2.25}{\mathrm{Mn}}_{0.75}\mathrm{Ga}$. ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{G}\mathrm{a}$ exhibits half metallicity along certain high-symmetry directions of the Brillouin zone. For ${\mathrm{Ni}}_{2}\mathrm{Mn}\mathrm{Ga}$, the total and Mn local moments obtained from Compton scattering are in excellent agreement with theory.