Study On The Magnetic Properties Of Nano-wire Arrays Prepared By Template Synthesis Method

Anodic aluminium oxide membrane(AAO)which is fabricated by anodic oxide of Al not only has a simple process but also contains uniform parallel pores and high pore density. Furthermore, the pore diameter is controllable according to practical needs. These characteristics allow the use of AAO as template. Alumina template-synthesized one-dimensional nano-structured material has attracted many researchers and has been studied deeply in recent years.(1) Template is the base on preparing nano-wire arrays, so in this dissertation, the fabricating method of AAO template was researched hi detailed. The anodic oxide film formed in different electrolyte was observed by Atomic Force Microscopy(AFM) and Emission Field Scanning Electron Microscopy(EFSEM).The factors which affect the pore distributed orderliness were also discussed. Through experiments ,we found that the structure of Al is a main factor, the ordered distributed pore in a large area only be obtained from high pure Al; Compared with one-step method, Two-step method could get ideally ordered hexagonal pore arrays easily. The template with pore diameters ranging from 40 to 140 nano-meters, and with a density of pores ranging from 50×109 to 40×109/cm2 have been obtained in sulphuric, oxalic or phosphoric acid. The thickness of membrane determined the depth of pore which also have an effect on the aspect ratio(ratio of length to diameter)of nano-wire, so the effect of voltage, temperature, time, concentration on the thickness of membrane was also discussed. The AAO membrane fabricated in our lab is very suitable to be used as template.(2) Fabrication of nano-wire arrays. Through electrodepositing, we fabricate Fe, Co, Ni, Fe-Co, Co-Ni nano-wire arrays. The crystal orientation of Cu nano-wire arrays were discussed according to the X-ray diffraction spectrum. It was found that Cunano-wires have (111). (200). (220) > (331) preferred orientations during growth and the structure is hexagonal .EFSEM analysis showed nano-wires were continuous and had the unique diameter about 50nm which is same as the pore diameter of AAO template; the length of nano-wires ranges from 300nm to several Mm. Their aspect ratio is more than 800. PMMA testing gave the magnetic remnant loops of the magnetic nano-wire arrays mentioned above. Enhanced coercivity(about 2259Oe) and remanent magnetization up to 92% of the saturation magnetization have been observed in Fe nano-wire arrays, Fe and Fe-Co alloy has good perpendicular magnetic recording properties. The easy magnetization axis of this system is perpendicular to the membrane.(3) Setting up the instruments for fabricating of multi-layer nano-wire arrays. Our research group designed and conceptualized three-electrode electrodepositing system controlled by compute, which can control export pulse voltage and time. In addition, the testing device for GMR was also given in the end of the dissertation.