This dissertation presents methods for wideband characterization and modeling of magnetic materials and structures over a wide frequency range (dc to a few GHz). A method for modeling the thick film inductor structures at high frequencies is presented in this dissertation. The thick film inductor under test is printed and located in shunt connection at the end of a reference transmission line. Time Domain Reflectometry (TDR) technique is used to measure the response waveform from the inductor under test. The response from a short circuit at the location of the inductor is acquired as the reference waveform. The two acquired waveforms are then transformed into the frequency domain using the Fast Fourier Transform algorithm (FFT). The reflection coefficient is then computed as the ratio between the Fourier Transforms of the response and reference waveforms. From the information contained, the complex impedance of the structure under study can be calculated. This information is used for modeling that structure by fitting the data to the network model using the computer network analysis program. Experimental and simulated response waveforms are compared and brought to a close match by changing the model components values. A cavity-like sample holder filled with ferrite material ls proposed in this dissertation to measure the complex permeability of the magnetic material filling this cavity. The cavity walls are deposited on a coaxially shaped sample using thick film techniques. The reflection coefficient from the cavity under study is measured by adapting the cavity to the end of a transmission line. The full field analysis of this proposed configuration is used to determine a relationship between the complex permeability of the ferrite material and the measured reflection coefficient. The method of moments ls used to achieve this task. Computer simulation experiments are performed to test the sensitivity of the technique and to predict the performance over the desired frequency range. Actual experimentation as well as verifications of these measurements are conducted to verify the merit of the proposed technique. / Ph. D. / incomplete_metadata

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In this presentation it is demonstrated that the unique magnetic properties of superparamagnetic cobalt-spinel ferrite nanoparticles can be employed in several novel applications. A method to selectively capture and remove pathogens from infected organisms to improve longevity is presented. Evidence is provided to show that automated methods using modified forms of hemofiltration or peritoneal dialysis could be used to eliminate the particle/pathogen or particle/infected cell conjugates from the organism postoperatively. It is shown that disparately functionalized nanoparticles can be used in concert as drug carrier and release mechanisms. Lastly, we provide preliminary evidence to support the use of magnetic nanoparticles for controlling reaction kinetics.

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A matrix of variably processed Fe-30at%Ni was deposited with variations in laser travel speeds as well and laser powers. A complete shift in phase stability occurred as a function of varying laser travel speed. At slow travel speeds, the microstructure was dominated by a columnar fcc phase. Intermediate travel speeds yielded a mixed microstructure comprised of both the columnar fcc and a martensite-like bcc phase. At the fastest travel speed, the microstructure was dominated by the bcc phase. This shift in phase stability subsequently affected the magnetic properties, specifically saturation magnetization. Ni-Fe-Mo and Ni-Fe-V permalloys were deposited from an elemental blend of powders as well. Both systems exhibited featureless microstructures dominated by an fcc phase. Magnetic measurements yielded saturation magnetizations on par with conventionally processed permalloys, however coercivities were significantly larger; this difference is attributed to microstructural defects that occur during the additive manufacturing process.

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