Phonon softening in Ni-Mn-Ga alloys - art. no. 024305

The TA(2) phonon dispersion curves of Ni-Mn-Ga alloys with different compos itions which transform to different martensitic structures have been measur ed over a broad temperature range covering both paramagnetic and ferromagne tic phases. The branches show an anomaly (dip) at a wave number that depend s on the particular martensitic structure, and there is softening of these anomalous phonons with decreasing temperature. This softening is enhanced b elow the Curie point, as a consequence of spin-phonon coupling. This effect is stronger for systems with higher electronic concentration.