Magnetization reversal and dynamic behaviour of patterned ferromagnetic nanostructures

Abstract

Patterned ferromagnetic nanostructures have attracted remarkable research interest in the past decades due to their potential applications in memory, logic and microwave devices. In this thesis, a comprehensive investigation on magnetization reversal process and dynamic behavior of various ferromagnetic nanostructures is presented. Firstly, the magnetic behavior of rectangular and circular Ni80Fe20 ring arrays is systematically compared. The corners and shape anisotropy of rectangular rings was identified as a key factor in modifying the magnetization reversal paths and the observed ferromagnetic resonance (FMR) modes. Secondly, a fabrication technique for making a range of self-aligned bi-component and thickness-modulated nanostructures is presented. Unique magnetic behavior of the resulting bi-component (Ni80Fe20/Fe) nanostructures was described and modeled. Thirdly, vortex dynamics in thickness-modulated Ni80Fe20 disk was investigated. The vortex core location can be systematically controlled via the geometry. Moreover, vortex propagation and annihilation can be detected by their FMR modes. Lastly, simultaneous control of vortex chirality and polarity using [CoPd]n/Ti/Ni80Fe20 thickness-modulated disk is demonstrated. The dynamic behavior of the single multilayer disk was also investigated using micro-focused Brillouin light scattering spectroscopy.