| As electronic information science and technology development, ask us to pursue higher storage density and smaller storage unit, as the carrier of information--magnetic recording media, the storage density to be improved. Because of magnetic nanowire arrays in high-density vertical magnetic recording and the development of a new record in memory has a tempting application prospect, the research of magnetic nanowire arrays on this aspect has become increasingly active in recent years.In this paper, Porous anodic aluminum oxide (AAO) templates with highly ordered and controllable pore size have been successfully prepared by a two-step anodization technique. The appearance and structure of templates were characterized using field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD).Base on the experiment result, the effect of processing parameters (such as type of electrolyte, anodization voltage, temperature and reaming time) on the quality of AAO templates has been analyzed. The suitable processing conditions have been obtained to prepare high quality AAO templates with different pore diameter, the formation mechanism of AAO were also discussed; highly ordered uniform Ni, Co and Fe nanowire arrays have been successfully fabricated in homemade AAO templates by pulse electrodeposition method. The morphology, structure of nanowires arrays have been characterized by XRD, FE-SEM, and transmission electron microscope (TEM). The magnetic properties of nanowire arrays have been investigated by Physical Property Measurement System (PPMS). The effert of diameter to the magnetic properties of nanowire arrays were also investigated by analyzing the magnetic properties of nanowire arrays with different diameters; highly ordered uniform Ni/Co, Co/Fe and Ni/Fe nanowire arrays have been successfully fabricated in AAO templates use Dual bath by pulse electrodeposition method. The morphology, structure and magnetic properties of nanowires arrays have been characterized.The results showed that the suitable processing conditions to prepare high quality AAO templates when oxalic acid as the electrolyte is: the concentration of oxalic acid solution is 0.3mol/L, anodization voltage is 40V, the temperature controlled below 10℃and the anodization time is 16h; when sulfuric acid as the electrolyte the best processing conditions is: the concentration is 0.3mol/L, anodization voltage is 25V, the temperature controlled below 5℃and the anodization time is 16h.The diameters of Ni, Co and Fe correspond to the pore diameter of the AAO templates and the nanowires are uniform in diameter. Ni, Co and Fe nanowires arrays all have single crystal structure. The Ni nanowires have preferred orientation along the [220] direction, the direction is [100] for Co nanowires and [110] for Fe nanowires. The metal spontaneously grow along the preferred orientation in small pore size AAO template is due to the extrusion and restriction effect of the wall of AAO templates. The magnetic properties of nanawire arrays with different diameters indicate that the nanowire arrays with small diameter have obviously perpendicular anisotropy. The perpendicular anisotropy of nanowire arrays increases with the decrease of the diameter. A high squareness (up to 0.94) is obtained for Ni nanowire arrays with 40nm in diameter, while the nanowire arrays with 80nm in diameter don't have obviously perpendicular anisotropy. This is because the highly preferred in nanowires with small diameter owes to the shape anisotropy of nanowires.Multilayer nanowires have a structure with obvious two layers, the crystal structure and growing direction of each layer correspond to the elementary substance nanowires. The magnetic properties of multilayer nanawires indicate that the nanowire arrays also have obviously shape anisotropy similar to the elementary substance nanowire arrays. Multilayer nanowire arrays can also take to use as high-density vertical magnetism recording materials.
|
PDF Full Text Request