Microstructure and magnetic properties of Ni-rich Ni54Mn25.7Ga20.3 ferromagnetic shape memory alloy thin film

A Ni54Mn25.7Ga20.3 ferromagnetic shape memory alloy thin film has been fabricated by using the RF magnetron-sputtering technique. The structure and magnetic properties of the film were systematically investigated. The results show that the film is in ferromagnetic martensite state at room temperature with the Curie temperature (Tc) of about 370 K. The saturation magnetization (Ms) of the film reaches 45 emu/g at 300 K, which is about 80% as large as that of Ni–Mn–Ga bulk material. The magnetization hysteresis loops significantly depend on temperatures. The residual magnetization (Mr) and the coercive force (Hc) increase with decreasing temperatures. The grains homogeneously distribute in the film. The microstructure of the film consists of martensite plates. The interface between the martensite variants is clear and straight, indicating a good mobility.