The effect of field cooling and field orientation on the martensitic phasetransformation in a Ni2MnGa single crystal

The temperature and field dependence of the magnetization in a Ni2MnGa sing le crystal was measured using a magnetometer with an applied field oriented in the [001] and [011] directions, respectively, of the parent cubic phase . It was found that the magnetic field magnitude and direction could be use d to determine the magnetization of the sample during a thermal transformat ion from the austenitic phase to the martensite phase. This is explained in terms of a magnetic field induced growth of the twin variant having a favo rable orientation to the external magnetic field. A model to interpret the magnetic response in terms of aligned twin variants in the shape memory mat erial is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00) 93208-0].