UC San Diego

This dissertation explores the nanofabrication and characterization of anisotropic metallic nanomaterials. Employing both bottom-up and top-down fabrication techniques, the chemistry and crystal structure of metals were exploited to create an assortment of anisotropic nanomaterials ranging from gold nanocrystals to nickel nanowires to CoFeB/MgO thin films. We investigate the role of anisotropy on the physical properties in these nanomaterials. The anisotropy arises from the combined effects of the shape, crystal structure and symmetry breaking at interfaces. The effect of anisotropy on properties such as strain, magnetic anisotropy and micromagnetic configuration were investigated. A variety of characterization techniques ranging from imaging, simulations and magneto-transport measurements were employed. We first study the strain distribution within anisotropic nanocrystals associated with its shape. We further study the interplay between the nanocrystals and the substrate on the strain distribution. We then study the relation between the strain, magneto-crystalline anisotropy and shape on the magnetic response of Ni nanostructures, including magnetic vortex configurations in Ni nano-cube and nano-wires. This interplay leads to complex domain patterns and could enable novel bio-magnetic applications and magnetic-superconducting devices. Lastly we explore ion-irradiation as a tool to modify the interfaces of ultra thin films with which we can tailor the magnetic anisotropy.