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Particle Size and Surface Charge Induced Variations in Magnetic Properties of Metallic and Semiconducting Nanostructures Open Access

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Novel physical phenomena arise when the size of a magnetic system is reduced from bulk to the nanoscale regime. New possibilities in magnetization dynamics, negative remanent magnetization and charge-induced response of magnetization, which are respectively driven by the reduced energy barrier and the increased surface to volume ratio, are presented.The scope of this dissertation is to investigate the particle size and surface charge induced variations in magnetic properties in strategically selected magnetic nanostructures. The proposed dissertation is highly interdisciplinary in that it spans the fields of electrical engineering, materials science, physics, mathematics, and chemistry. The applied research methodologies include chemical synthesis of nanostructure, structural and magnetic characterization, numerical modeling and analytical derivation, and design and construction of in-situ experimental instruments. The aim of this dissertation is to explore the connections between various novel magnetic phenomena and their characteristic length scales. The detailed objectives include gaining new insights into i) magnetization dynamics in monodispersed 3d metallic and 4f semiconducting magnetic nanoparticles, ii) an unusual behavior of negative remanent magnetization, also known as inverted hysteresis loop or negative coercivity, observed in 4f semiconducting monodispersed magnetic nanoparticles, and iii) electronically tunable variations in magnetization in magnetic thin films.The dissertation will present i) the development of a Modified Preisach-Arrhenius model and the derivation of an analytical formula for the prediction of time reliability of magnetization state, ii) verification of the negative remanent magnetization in homogeneous nanoparticles and the explanation for the origin of this phenomenon, and iii) the realization of dynamic and reversible control of magnetic properties of magnetic thin films via applied electrostatic field.

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