Magnetotransport and magnetooptical properties of ferromagnetic nanostructures

Abstract

Ferromagnetic (FM) nanostructures have attracted great research interest in recent years due to their potential applications in magnetic random access memories (MRAM) and logic devices. With the use of advanced lithography techniques and nano-characterization tools, this thesis attempts to enhance the current fundamental understanding in magnetic nanostructures. In the first part of the thesis, a systematic control of vortex chirality in FM nanodots using in-plane magnetic field and lattice dot configurations is presented. A theoretical model has also been developed to investigate the magnetostatic interactions between the patterned nanodots which primarily govern the chirality of the vortex states. Second part of the thesis presents the formulation of a resistor network model to study the magnetization reversal process in individual FM ring elements. A novel non-local probing technique has also been developed to investigate the reversal behaviour in the entire ring structure, without being dependent on the contact geometry. This technique has been further utilized to control the vortex state stability in individual elliptical rings by engineering the position and orientation of magnetostatically coupled magnetic elements. Lastly, an extensive study of the effect of domain wall pinning on the vortex formation in triangular rings for both FM and antiferromagnetic (AFM) multilayer structures is presented as they are the potential candidates for magnetic logic devices.