Date of Award

Summer 2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Micro and Nanoscale Systems

First Advisor

Niel Crews

Abstract

This dissertation details a novel method to fabricate magnetic sensors using nanowire giant magnetoresistance (GMR) thin films. In 1988, Albert Fert and Peter Grünberg both independently discovered a new physical phenomenon called GMR. GMR is a quantum mechanical effect found in thin film materials that are composed of alternating nanoscale ferromagnetic and non-magnetic conductive layers. When a GMR material is in the presence of a magnetic field, a change in electrical resistance is observed. The GMR effect has been utilized to produce magnetic sensors that have been used in a variety of applications, such as computer hard drive read heads, position sensors, proximity detectors, and biosensing devices. Although there are other types of magnetic sensors that have greater sensitivity and lower magnetic detection limits, such as the SQUID magnetometer, GMR sensors have more commercial potential due to their small size, low power requirements, low fabrication cost, and reproducible operation in very narrow magnetic ranges.

The purpose of this research is to create nanowire GMR thin films for magnetic sensing applications. Using an electrodeposition technique, CoNiFeCu/Cu multilayer nanowires are fabricated inside of anodic aluminum oxide (AAO) templates. Parameters, such as electrolyte concentration, current density, and deposition times were studied in a previous study to determine the values that achieve the highest change in resistance in an applied magnetic field. After GMR nanowires are fabricated inside the template, they are removed and transferred to flexible and transparent polyethylene terephthalate (PET) substrates using a variety of techniques including vacuum filtration and metering rod methods. This will be the first study on GMR nanowire thin films for magnetic sensors that are inexpensive, transparent and flexible.

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