Stabilization of Martensite and Austenite Phases and Realization of Two-way Martensitic Transition in Co-Ni-Ga Ferromagnetic Shape Memory Alloy Nanoparticles

Researchers synthesized three compositions of Co-Ni-Ga alloy nanoparticles using a template-free chemical route and examined their structure, morphology, shape-memory behavior, and magnetism. XRD measurements versus temperature show that one composition, Co36Ni36Ga28, is martensite at room temperature and fully transforms to austenite at about 1000 K; on cooling, it returns to martensite, demonstrating a two-way martensitic transition in the nanoparticles. For dual-phase (M + γ) nanoparticles, the abstract reports that the γ phase does not influence the martensitic transition. The γ phase can be introduced in an austenite composition when heated to 1073 K, and the materials are described as ferromagnetic because Curie temperatures are higher than the martensitic transition temperatures. The authors conclude these nanoparticles could be candidates for low- and high-temperature nanoactuators and other ferromagnetic shape memory applications.