Electrodeposition of magnetic nanowires and nanotubes

Abstract

The current perpendicular to the plane giant magneto-resistance (CPP)-(GMR) effect makes multilayered nanowires of huge interest as magnetic sensor materials. GMR showing multilayer nanostructures are composed of alternating ferromagnetic and nonmagnetic nanometric layers. The giant magnetoresistance (GMR) property is described as a change in electrical resistance when an external magnetic field is introduced. Electrodeposition is the most efficient method for fabricating magnetic nanowires. In addition to the cost-effectiveness, electrodeposition is one of the few methods that can overcome the geometrical restrictions of inserting metals into very deep nanometric recesses, making it the favored method for nanowire and nanotube fabrication. In this thesis, the quaternary FeCoNiCu alloy system was investigated in order to electrodeposit multilayered nanowires/nanotubes for GMR effect. The choice of CoNiFeCu quaternary system allows the flexibility to optimize the magnetic property (GMR) by varying deposit composition. This study demonstrates the ability to fabricate multilayered CoNi(Fe)Cu/Cu nanowires using different templates: polycarbonate membranes (PC) and porous alumina filters (AAO). Layer thicknesses were controlled and varied for commercially viable GMR results. The effect of electrolyte additives and concentration was demonstrated to have an effect on the GMR. Greater than 10 % GMR, at room temperature and at small magnetic fields (< 0.5 Tesla), is reported for the first time in CoNiCu/Cu and CoNiFeCu/Cu nanowires. CoNiCu nanotubes in PC membranes were also fabricated for the first time. Conditions for electrodepositing multilayered nanotubes that exhibit GMR has been established and is a pioneering effort in the field.