Isomagnetic martensitic transformation in Ni2MnGa alloys

An effect of the magnetic field on the martensitic transformation and the change in the martensitic variants of the alloy Ni2MnGa containing (at%) 49.6 Ni, 28.4 Mn and 22.0 Ga was studied using X-ray diffraction. It is shown that the applied magnetic field induces martensitic transformation and initiates the development of a preferential martensitic variant. These processes are extended in time, which resembles the isothermal martensitic transformation observed in iron-based alloys. The kinetics of transformation under magnetic field and the after-effect when the field is taken out are studied. The kinetics is shown to depend on the orientation of the applied field in relation to the direction of easy magnetization [1 0 0]. The strain induced by the magnetic field is measured and the time dependence of the strain is Found in consistence with the results of X-ray diffraction study. (C) 2000 Elsevier Science B.V. All rights reserved.