Phase Transformations and Magnetostriction in Ni–Mn–Ga Ferromagnetic Shape Memory Alloys

Composition dependence of martensitic transformation and ferromagnetic transformation behavior has been investigated for Ni–Mn–Ga ferromagnetic shape memory alloys in a polycrystalline state. DSC measurements were performed to determine the transformation temperatures. Magnetic properties were studied by VSM. It was revealed that martensitic transformation temperature depends strongly on valence electron concentration, e⁄a, of the alloys, while ferromagnetic transformation temperature exhibits only mild dependence. Room temperature magnetization was found to decrease with increasing e⁄a. Magnetostriction was measured for Ni–23.1Mn–24.6Ga alloy as a function of magnetic field and temperature. The largest magnetostriction was observed near the martensitic transformation temperatures.