Gregory Kozlowski (Advisor), Sarah Tebbens (Committee Member), Zafer Turgut (Committee Member)
Master of Science (MS)
Surface effects on critical dimensions of ferromagnetic nanoparticles were studied. Algebraic equations were derived and numerically solved for critical radius RC2 of ferromagnetic nanoparticles describing the transition between single- and multi-domain magnetic structure. Results were analyzed to illustrate the effect of surface parameters related to saturation magnetization a, exchange interaction ß, and anisotropy KS on the critical radius of nanoparticles with a core value of anisotropy KV. Available experimental data for MnBi, FePt, and CoPt or for Fe nanoparticles were used as examples of nanoparticles with high and low values of KV, respectively. Our studies clearly show that discrepancies existing between theoretical and experimental values for RC2 could be explained readily by modification of magnetic surface parameters. The equation for lower critical radius RC1 from a single domain structure to superparamagnetic phase has been derived to study the effect of the surface parameter KS on its critical radius. This equation for RC1 was solved analytically and numerically for high and low core anisotropy KV in magnetic nanoparticles. The results were examined for Fe as an example of low KV magnetic nanoparticles, and for MnBi, FePt, and CoPt as examples of strong KV nanoparticles. Discrepancies between theoretical results for RC1 and available experimental data again can be explained by changes of magnetic properties of nanoparticles near their surface.
Department or Program
Department of Physics
Year Degree Awarded
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