Kinetics of Magnetoelastic Twin-Boundary Motion in Ferromagnetic Shape-Memory Alloys

We report the kinetics of twin-boundary motion in the ferromagnetic shape-memory alloy of Ni-Mn-Ga as measured by in situ high energy synchrotron diffraction. The temporal evolution of twin reorientation during the application of a magnetic field is described by thermally activated creep motion of twin boundaries over a distribution of energy barriers. The dynamical creep exponent mu was found to be similar to 0.5, suggesting that the distribution of energy barriers is a result of short-range disorders.