Structure and phase transformation of ferromagnetic shape memory alloy Ni/sub 49/Mn/sub 30/Ga/sub 21/ fine particles prepared by spark erosion

Ni/sub 49/Mn/sub 30/Ga/sub 21/ fine particles were prepared by spark erosion. Most of the particles are spheres with sizes ranging from about 5 nm to 100 (mu)m. The particles have martensite structure at room temperature as indicated by X-ray diffraction (XRD). Measurements of the temperature dependence of the magnetization and high-temperature XRD patterns demonstrated that the particles undergo a martensite - austenite phase transformation in the range 35(degree)C-70(degree)C during heating, with ~10(degree)C hysteresis for the austenite - martensite transformation upon cooling.