Structure transition and magnetism of bcc-Ni nanowires

Body-centered-cubic (bcc) Ni nanowires were successfully synthesized by multistep ac electro-deposition on anodic aluminum oxide templates. bcc-Ni is ferromagnetic with a lattice constant of 0.288 nm, and bcc-Ni to fcc-Ni phase transition occurs under heat treatment. Magnetic measurements suggest that the ferromagnetic transition of bcc-Ni nanowires involves a structure change evolving from bcc to fcc in the magnetic-ordering process. Furthermore, the processes of structure transition in bcc-Ni nanowires under the heating conditions were observed in situ using transmission electron microscopy. In addition, our work also establishes that fcc-Ni nanowires and bulk Ni have only a ferromagnetic transition at the Curie point, involving no crystal structure change.