giant, magneto-impedance, NiFe, CoSiB, thin film, magnetic


Recently, the giant magneto impedance (GMI) effect has been studied extensively because of its potential applications in sensor elements. The focus of this thesis work is to explore different compositions and processing conditions for CoSiB and NiFe thin films to obtain the soft magnetic properties and to evaluate their potential use in GMI sensor applications. Prior to this study, an MH Looper was constructed, which was extremely important and provided the basic magnetic characterization of the many ferromagnetic thin films deposited during this work. The CoSiB films were co-sputter deposited in an ultra high vacuum chamber. Films with different relative compositions of Co, Si and B were deposited by varying respective target powers. Different substrate bias conditions were also studied. Also, NiFe films were studied by varying relative composition by variation of target powers and also by variation deposition pressure. The effect of annealing was also studied. The magnetic and electrical characterization of these films was done using the MH Looper, Quad-pro four-point probe resistivity measurement, and Low Frequency Impedance analyzer HP4192A. Finally, CoSiB films with soft magnetic properties were obtained with optimized set of deposition parameters. A sample for GMI measurement was prepared, consisting of a multilayer thin film structure: CoSiB 200nm/ Cu 400nm / CoSiB 200nm. A serpentine pattern was generated on this film by photolithography technique. After obtaining the pattern, GMI studies were performed using LF impedance analyzer. This instrument was capable of providing the drive frequency in the range of 5Hz to 13MHz, but the impedance mis-match of the test fixture limited useful measurements to 9MHz. The highest GMI ratio observed was 6.2% at a 21 Oe longitudinal magnetic bias field at an 8MHz drive frequency. Transverse permeability measurements were performed by the use of two magnetic field axes of the MH Looper. The permeability behavior of the device reflects the impedance behavior with the external field. Permeability measurements were also performed on NiFe GMI Device with NiFe 600nm/ Cu 1200nm / NiFe 600nm sandwich structure. This sample was not successfully patterned and hence the impedance measurements could not be performed. Correlation of the magnetic properties of the structures was studied with the impedance responses.


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Graduation Date





Sundaram, Kalpathy B.


Master of Science in Electrical Engineering (M.S.E.E.)


College of Engineering and Computer Science


Electrical and Computer Engineering

Degree Program

Electrical Engineering








Release Date

January 2006

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)