Electrodeposition and magnetic properties of three-dimensional bulk and shell nickel mesostructures

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Description/Abstract

In this paper we demonstrate the electrodeposition of nickel, a common ferromagnetic material, in various magnetically desirable shapes including nanowires, nanoparticles and highly faceted shells. In order to obtain three dimensional mesostructures, the electrochemical deposition of nickel was performed on highly oriented pyrolytic graphite (HOPG) under different electrolyte composition and deposition potential conditions. Under potentiostatic deposition at one distinct potential negative with respect to the reversible potential of nickel, three stages of nucleation and growth take place leading to a complex morphology of deposits. However, dual-pulse potential deposition and electrodeposition in low pH solutions causing hydrogen evolution, lead to nickel deposits in the form of nanowires and nanoparticles with the complete absence of a faceted morphology. Highly faceted nickel shells were electrodeposited via a dual-bath method on prefabricated silver mesocrystals as 'template' electrodeposited on HOPG. Magnetic properties of faceted three dimensional nickel shells reveal clear signatures of facets of mesocrystals in the form of sharp steps in measured hysteresis loops and a strong magnetic anisotropy with respect to applied field direction.