Composition, structure and magnetic properties of sputter deposited Ni–Mn–Ga ferromagnetic shape memory thin films

Polycrystalline Ni–Mn–Ga thin films were deposited by the d.c. magnetron sputtering on well-cleaned substrates of Si(1 0 0) and glass at a constant sputtering power of 36 W. We report the influence of sputtering pressure on the composition, structure and magnetic properties of the sputtered thin films. These films display ferromagnetic behaviour only after annealing at an elevated temperature and a maximum saturation magnetization of 335 emu/cc was obtained for the films investigated. Evolution of martensitic microstructure was observed in the annealed thin films with the increase of sputtering pressure. The thermo-magnetic curves exhibited only magnetic transition in the temperature range of 339–374 K. The thin film deposited at high sputtering pressure of 0.025 mbar was found to be ordered L21 austenitic phase.