Magneto-thermal shape memory effect in Ni-Mn-Ga

A way to produce shape memory in Ni-Mn-Ga alloys is proposed based on the combined action of the magnetic field and heating. A sample is magnetized under applied magnetic field, which results in the magnetic-field-induced strain caused by the reorientation of martensitic domains so that the tetragonal axis c (axis of easy magnetization) is oriented in direction of the applied field. Thereafter the field is switched off and the sample is heated above the Curie temperature and cooled to the start temperature of the experiment, which leads to the full recovery of the size and structure existing before the action of magnetic field. This effect is explained based on the data of x-ray diffraction studies. (C) 2002 American Institute of Physics.