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Studies on the Preparation and Magnetic Properties of FePd Nanowire Arrays

Author: XuZhiBing
Tutor: TangShaoLong
School: Nanjing University
Course: Condensed Matter Physics
Keywords: Nanowire arrays Fe-Pd Anodic alumina template Template Magnetic studies Porous alumina Solution Morphology Nanomaterials Magnetic properties Electrodeposition Magnetron sputtering Energy dispersive spectroscopy Metal film Growth Mechanism Thin film layer A perpendicular magnetic recording medium Metallic nanowires Preparation Size
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 28
Quote: 0
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Abstract


In this dissertation, we focus on the research of FePd nanowire array about its preparation, morphology, crystalline structure, and magnetic properties. By developing the fabricating technology of the anodic aluminum oxide (AAO) templates on silicon chip, the electro-deposition of free-standing FePd nanowire arrays was achieved on the templates. We scrutinized the magnetic properties and phase transition in all samples that are as-deposited, annealed with AAO templates, or annealed without AAO templates. The compositions of FePd nanowircs were determined by energy dispersive X-ray spectroscopy(EDX), the morphologies were studied using scanning electron microscope (SEM) and atomic force microscope (AFM), the crystal structures were characterized by X-ray diffractometry (XRD), and the magnetic measurements were performed on vibrating sample magnetometer (VSM). The primary results are as follows:1. The preparation and characterization of AAO templates on silicon substrateThe transfixed AAO templates was prepared by anodizing the Ti/W/Al multilayer with the silicon substrate in dicarboxyl. By studying the time-dependent current (IT) curve, we propose based on the steady state pore growth mechanism that the formation of porous structure was comprised of three stages:the formation of barrier layer, the pore nucleation, and the steady state structure of pore. The as-synthesized AAO templates exhibited a hexagonal structure with an average pore size of about 75 nm, in accordance to the templates prepared by directly anodizing aluminum chip. The porous tungsten-oxide film was compatible to the structure of AAO templates and would therefore be suitable for the electrode in the electro-depositing of nanowires.2.The fabrication and magnetic properties of FePd nanowire arraysBy using AAO templates anodized from Ti-W-Al multilayer, the electro-deposition of FePd nanowires was carried out in the aqueous mixture of Pd(NH3)4Cl2, Fe(C7H6O6S)2 and (NH4)2SO4. A series of homogeneous FePd nanowire arrays were obtained by applying different dc voltages in the I-T mode of the electro-chemical analyzer. The influence of the applied electric voltage on the composition of nanowires was investigated through the analysis of EDX measurement. The magnetic properties of the as-deposited samples and the as-annealed ones with/without AAO templates were studied using vibrating sample magnetometer (VSM). Parts of the samples annealed at 600℃exhibited a wasp waist-like hysteresis loop comprised of two magnetic phases, which showed an obvious crystallographic orientation. The formation of FePd L10 phase was inferred based on the variation of coercivity before and after annealed. The comparison between the as-annealed samples with and without AAO templates revealed that the templates did not have much influence to the phase formation during the annealing process.

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