The electrodeposition of NiFe nanowires-with the length ∼3.0 μm and diameter 200 nm-using the porous anodized aluminum oxide (AAO) templates on the sputtered Au-back electrode (300 nm) using sulfate/chloride electrolyte solution and potential pulsed deposition. The electrode area of Au-AAO template, determined by the reversible one-electron transfer oxidation of K 4 Fe(CN) 6 , used as a probe in CV, was found to be ∼2.4 times larger than Au-thin film electrode. The anomalous codeposition phenomenon known as a ,,volcano" type curve-with a maximum in Fe-content in NiFe as a function of the applied potential-was observed in the literature. The observed results were explained through the limited mass transport of Fe +2 ions after the peak. This explanation is partially correct, but not complete. The electrodeposition of NiFe nanowire in this work resulted in a similar "volcano" type curve. The alternative explanation of anomalous codeposition-through the surface concentration of H + dependent adsorption/desorption of FeOH + and NiOH + electroactive species-was proposed. The electrodeposition of NiFe nanowire arrays using a designed pulse potential method produced fcc NiFe nanowires with 5-55% Fe with controlled composition, length, and uniformity.The distinct decrease of parallel coercivity of NiFe nanowire arrays having the same length was observed with increase of Fe-content in NiFe, which also correlates with the increase of their magnetic saturation. 12 The studies on magnetic properties of NiFe nanowire arrays were intensified during last 15 years. [13][14][15][16][17][18][19][20] The electrodeposition of NiFe alloys exhibits a phenomenon known as an anomalous codeposition, which is characterized by the anomaly that less noble metal, i.e. Fe, deposits preferentially. 21 The extent of anomalous codeposition can be evaluated by the "selectivity ratio" (SR), which is defined as an atomic ratio of Fe/Ni in the deposit to the molar ratio of Fe +2 /Ni +2 in the electrolyte. 22 The SR is dependent on solution condition (pH, presence of organic additives, concentration of electrolytes, temperature, etc), method of electrodeposition (constant current density, controlled potential, pulsed current or potential), and the thickness of deposit. The value of SR ranges from 1.0 (for non-anomalous codeposition) to 15 (for anomalous codeposition). The variation of composition of NiFe films affects the following properties of deposit: (i) stress, 23 (ii) magnetostriction, 24 (iii) crystal structure, 25 and (iv) grain size. 26 Thereby, the resulting changes profoundly influence the magnetic behavior of electrodeposited NiFe alloys, which was demonstrated recently. 27The present work describes the method of electrodeposition of NiFe nanowires into anodized aluminum oxide (AAO) templates with the controlled elemental composition using designed potential pulse electrodeposition. We report here a new explanation for the observed anomalous codeposition of NiFe in nanowires, through the surface concentration of H + dependent adsorption/...
Abstract:The magnetic characteristics of FINEMET type glass-coated nanowires and submicron wires are investigated by taking into account the structural evolution induced by specific annealing all the way from a fully amorphous state to a nanocrystalline structure. The differences between the magnetic properties of these ultrathin wires and those of the thicker glass-coated microwires and "conventional" wires with similar structures have been emphasized and explained phenomenologically. The domain wall propagation in these novel nanowires and submicron wires, featuring a combination between an amorphous and a crystalline structure, has also been studied, given the recent interest in the preparation and investigation of new materials suitable for the development of domain wall logic applications.
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