Effect of Annealing on the Magnetic Properties of Ni Nanowires Prepared by Using an Anodized Aluminum Oxide Template

We report the growth mechanism and the magnetic properties of Ni nanowires on an anodized aluminum oxide (AAO) template. The porous AAO was fabricated using a two-step anodization process. The Ni nanowires were grown by using DC pulsed and AC electrodeposition methods, and the Ni nanowires were more uniformly grown by using the AC electrodeposition method than by using the DC pulsed electrodeposition method. We also studied the magnetic properties of the Ni nanowires and the post-annealed Ni nanowires (at 600 ℃ in air). The annealed Ni nanowires showed smaller ferromagnetic saturation than the unannealed Ni nanowires. This result indicates that NiO existed in the Ni nanowires after the post-annealing process. In addition, the magnetic properties of the Ni nanowires at 5 K showed that the easy magnetization axis in the annealed Ni nanowires had rotated from the parallel to the nanowire surface to the perpendicular to that surface. Since the shape anisotropy of continuous Ni thin films favors the direction of the easy magnetization axis being parallel to direction of their surfaces, these results show that at low temperatures, the magnetic properties of Ni nanowires behave as those of continuous Ni thin films. KCI Citation Count: 0