Templates - Electrodeposition Preparation Of Magnetic Nanowire Arrays

Magnetic nanowire arrays, as an ideal candidate for future ultra-high density perpendicular recording media, are becoming the hotspot in modern magnetism field. There are countless reports on pure Fe, Co, Ni, and their alloys or oxides nanowires. But an important kind of magnetic material, rare earth - transitional metal (RE-TM) alloys, has been ignored. Using the home made anodic alumina oxide template (AAO template) as electrode, the pure Fe, Co nanowires and the Sm-Co nanowires were fabricated by electrodeposition. This thesis presents the following work:1. Highly ordered porous AAO template was prepared by two-step anodization method. The morphology and the structure of the AAO template were observed by atomic force microscope (AFM), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FE-SEM). The results showed: the template was highly ordered, it contained standard hexagonal pore arrays, and had the same hole-size; the pores were perpendicular to the membrane surface as well as paralleled with each other, and they were separated clearly without any crossing. The pore diameter can be adjusted between 40 to 140nm, and the depth of the pore can be controlled from dozens to hundreds microns.2. By AC deposition method, the pure iron and cobalt nanowires were made in the AAO template separately. The nanowire arrays were observed by FE-SEM. The photos showed that the nanowire arrays had a good linear structure, the same diameters, and large aspect ratio. The diameter of the wire arrays can be adjusted between 40 to 140nm, the lenth of wire arrays can be controlled from 10 to 35 microns, and the aspect ratio can be changed from 100:1 to 350:1. The surface of the wires was smooth. We used the X-ray diffraction (XRD) to detect the crystal structure of the iron and cobalt nanowires before and after the heat treatment. The XRD analysis indicated that the Fe crystal was body-centered cubic(BCC) structure and had different orientations; the heat treatment made the Fe crystal lay along with the direction of the Fe (110) crystalline face; the Co crystal was Hexagonal Closed Packed (HCP) structure and had different orientations; the heat treatment made most of the C axis of Co crystal grew along with the long axis of nanowires.3. The ordered Sm-Co nanowire arrays were electrodeposited in the AAO templates by AC and DC deposition separately. The FE-SEM observations indicated that the Sm-Co wires had the same good linear structure. The diameter of the wires also can be adjusted between 40 to 140nm, the lenth of wires can be controlled from 10 to 35 microns, and the aspect ratio can be changed from 100:1 to 350:1. And the wires proved to be amorphous structure by the X-ray diffraction technology. In addition, the Energy Dispersive Spectroscopy (EDS) analysis displayed: the rare earth element Sm was induced by the transitional metal Co, and they co-deposited from the aqueous solution together; compared with the DC deposition, the AC deposition is more conducive to the precipitation of Sm, the content of Sm can reached to 16.25w%. The research also told us: the PH value of the solution, the thickness of the barrier layer, the electrode and the planting tank affected the process of the Sm-Co deopositon greatly.