Spin correlations and a mesoscopic structure in Ni-Mn-Ga

Abstract

The mesoscopic structures of the Heusler alloys Ni 49.1 Mn 29.4 Ga 21.5 and Ni 2 MnGa are studied by small-angle polarized neutron scattering in the temperature range 15 < T < 400 K. The characteristic temperatures of phase transformations (ferromagnetic, martensitic, and premartensitic transformations) and the characteristic sizes of mesoscopic inhomogeneities in them have been determined. Differences in the spin dynamics of these phases and magnetic-nuclear interference upon neutron scattering have been revealed. The evolutions of the mesoscopic structures in the nonstoichiometric and stoichiometric alloys are found to be substantially different.