Effect of magnetic field on martensite transformation in a polycrystalline Ni2MnGa

Shape change (strain) was observed for a polycrystalline thermoelastic ferromagnetic shape memory alloy Ni–9.5at.% Mn–27at.% Ga upon cooling and healing with and without magnetic field. The shape change occurred at martensite start temperature, MS, and it was increased with increasing magnetic field. A large strain of 0.82% was observed when a magnetic field of 10 kOe was applied under a compressive stress of 126 MPa at 73 °C, several degrees above austenite finish temperature, Af. This magnetic field effect on changes of MS can be explained by a modified Clausius–Clapeyron relationship.