Epitaxial Ni–Mn–Ga films derived through high temperaturein situdepositions

Epitaxial films of the magnetic shape memory alloy Ni–Mn–Ga have been deposited on (100) YSZ substrates in a previously unexplored high temperature deposition regime. The temperatures employed encouraged the development of the desired micrometer-size highly twinned martensitic grain structure, where the loss of manganese and gallium at high temperatures was compensated for through enrichments to the target material. The films show the desired shape memory alloy properties of having a well-defined reversible martensitic transformation, centered around 85 °C, a room temperature martensitic phase with an in-plane saturation magnetization of 64 emu g−1, and a magnetically induced reorientation of the martensite variants which occurs at a low magnetic field of 400 Oe. The films also exhibit a hysteresis loop in the magnetic transition, a feature attributed to the overlap of the magnetic and structural phase transitions. The results suggest that the described in situ route provides a superior pathway to the formation of Ni–Mn–Ga films.