Epitaxial Ni–Mn–Ga films derived through high temperature in situ depositions

Abstract

Epitaxial films of the magnetic shape memory alloy Ni–Mn–Ga have been deposited on(100) YSZ substrates in a previously unexplored high temperature depositionregime. The temperatures employed encouraged the development of the desiredmicrometer-size highly twinned martensitic grain structure, where the loss of manganeseand gallium at high temperatures was compensated for through enrichments tothe target material. The films show the desired shape memory alloy propertiesof having a well-defined reversible martensitic transformation, centered around85 °C, a room temperature martensitic phase with an in-plane saturation magnetization of64 emu g−1, and a magnetically induced reorientation of the martensite variants which occurs at a lowmagnetic 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. Theresults suggest that the described in situ route provides a superior pathway to theformation of Ni–Mn–Ga films.