Coherent phonon dynamics at the martensitic phase transition of Ni_2MnGa
  We use time-resolved optical reflectivity to study the laser stimulated dynamics in the magnetic shape memory alloy Ni_2MnGa. We observe two coherent optical phonons, at 1.2 THz in the martensite phase and at 0.7 THz in the pre-martensite phase, which we interpret as a zone-folded acoustic phonon and a heavily damped amplitudon respectively. In the martensite phase the martensitic phase transition can be induced by a fs laser pulse on a timescale of a few ps. 
S. O. Mariager, A. Caviezel, P. Beaud, C. Quitmann, G. Ingold
cond-mat.mtrl-sci