Phonon dispersion in the ferromagnetic shape memory alloy Ni2MnGa studied by neutron spectroscopy

Neutron spectroscopy is an ideal technique to study the structure and dynamics of crystals. Previously obtained information from experiments for the austenitic f.c.c. phase of the ferromagnetic shape memory alloy Ni2MnGa with different compositions is summarized, and recently obtained inelastic neutron scattering data for the tetragonally distorted martensitic phase are presented. These new data were taken on a single crystal with stoichiometric composition. A single variant martensitic phase of the sample can be obtained by the application of magnetic fields while cooling through the transition. The measured phonon dispersion curves are compared with recently published ab initio zero temperature phonon dispersion calculations. The anomalous phonon behavior observed in both, the austenitic and martensitic phase is discusse