Twin boundary motion in NiMnGa upon pulsed field excitation

We studied the motion of twin boundaries in NiMnGa shape memory alloy bulk samples using time-resolved optical polarisation microscopy. The sample was excited by pulsed magnetic fields with variable rise-time. The restoring force to reset the sample, necessary for stroboscopic imaging, was set by applying mechanical stress along the long axis of the bulk sample perpendicular to the magnetic field. Upon decreasing the rise-time from 10 to 1 ms we found an increase of the twin boundary motion. This dependency of the actuation range on the pulsed field rise-time can be used in actuation devices to improve the magnetic field-induced strain by changing the field rise-time without having to change the repetition rate of the magnetic field.