Spin-dependent electron momentum density in theNi2MnSnHeusler alloy

Abstract

The spin-dependent electron momentum distribution in ${\mathrm{Ni}}_{2}\mathrm{MnSn}$ Heusler alloy single crystals was studied using 270 keV circularly polarized synchrotron radiation, through magnetic Compton profile measurements, on the high energy inelastic scattering beamline at SPring-8. The experiments were carried out for the three principal crystallographic directions [100], [110], and [111] at 10 K. The results show that the conduction electrons have a negative spin polarization of $0.34{\ensuremath{\mu}}_{B};$ the $3d$ spin moment on the nickel site was found to be negligible. A band structure calculation was performed including a hyperfine field study using the full potential linearized augmented plane wave (FLAPW) method, with the generalized gradient approximation (GGA) for the electronic exchange and correlation. The spin moment on the Mn site at 10 K was observed as $4.39{\ensuremath{\mu}}_{B}.$ The spin-dependent Compton profiles for the [100], [110], and [111] directions reported here show anisotropy in the momentum density, which is in good agreement with the FLAPW-GGA results, based on a ferromagnetic ground state. The hyperfine fields calculated were compared with previously calculated hyperfine field of ${\mathrm{Cu}}_{2}\mathrm{MnAl}$ and ${\mathrm{Co}}_{2}\mathrm{FeGa}$ Heusler alloys. From the comparison it is seen that the value of ${H}_{\mathrm{val}}$ (valence contribution to the hyperfine field) is roughly proportional to the spin polarization ${(m}_{s})$ of the s electrons at the X (Ni,Cu,Co) and Y (Mn of ${\mathrm{Ni}}_{2}\mathrm{MnSn}$ and ${\mathrm{Cu}}_{2}\mathrm{MnAl},$ Fe of ${\mathrm{Co}}_{2}\mathrm{FeGa})$ atom positions.