Very Low Potential Electrodeposition of Sm-Co Nanostructures in Aqueous Medium Using Hard Templates

Abstract

Arrays of SmCo nanowires (NW) and nanotubes (NT) with a diameter of 200 nm and different lengths are synthesized by electrodeposition into the nanopores of an alumina membrane. The potential applied during the synthesis largely determines the nanostructure morphology, its crystallinity and composition. Potentials investigated are between −0.8 V and −3.0 V; in the potential range between −0.8 V and 1.0 V, long and perfectly ordered nanowires are obtained with a composition close to that of the equilibrium Sm2Co17 phase in the binary alloy. For higher potentials, above −1 V, samples are nanotubes, 195 nm in external diameter and wall thickness of 30 nm with an equiatomical composition. Magnetic characterization reveals that all the nanostructures are soft ferromagnetic, with coercivity values below 60 mT. From the angular dependence of coercivity and the relative remanence it may concluded that in both, nanowires and nanotubes the magnetization reversal mechanism undergoes a transition from one at smaller angles, involving localized nucleation by curling, and further expansion of vortex-like domain walls. At higher angles, where the applied field is almost perpendicular to the NW/NT long axis, the mechanism changes to one involving nucleation by localized coherent rotation and further expansion of transverse Bloch-like walls.