Structural and magnetic phase transitions in Ni-Mn-Ga ferromagnetic shape-memory crystals

We detail crystal growth and characterization of Ni-Nln-Ga ferromagnetic sh ape-memory alloys (FSMA). Structural characterization includes x-ray Laue d iffraction and x-ray diffraction (XRD) using theta -2 theta scans. Differen tial scanning calorimetry (DSC) and DC magnetization measurements have been used to probe structural and magnetic phase transformations in these mater ials. For the first time, the temperature dependence of magnetic torque rev eals a variation of the magnetic anisotropy in stoichiometric Ni2MnGa cryst als. We also report on the effect of post-annealing on the martensitic phas e transition (MPT) temperature. A Ni52.7Mn22.6Ga24.7 crystal exhibits an on set of the transformation at 304 K. The temperature hysteresis during a hea ting-cooling process and the full width of the transition are observed to b e 2 and 10 K, respectively, for this crystal.