Structural and Magnetic Dynamics in the Magnetic Shape Memory Alloy   Ni$_2$MnGa
  Magnetic shape memory Heusler alloys are multiferroics stabilized by the correlations between electronic, magnetic and structural order. To study these correlations we use time resolved x-ray diffraction and magneto-optical Kerr effect experiments to measure the laser induced dynamics in a Heusler alloy Ni$_2$MnGa film and reveal a set of timescales intrinsic to the system. We observe a coherent phonon which we identify as the amplitudon of the modulated structure and an ultrafast phase transition leading to a quenching of the incommensurate modulation within 300~fs with a recovery time of a few ps. The thermally driven martensitic transition to the high temperature cubic phase proceeds via nucleation within a few ps and domain growth limited by the speed of sound. The demagnetization time is 320~fs, which is comparable to the quenching of the structural modulation. 
S. O. Mariager, C. Dornes, J. A. Johnson, A. Ferrer, S. Gr\"ubel, T.   Huber, A. Caviezel, S. L. Johnson, T. Eichhorn, G. Ja...
cond-mat.mtrl-sci