Ferromagnetic and Exchange Bias Studies in the Diluted Magnetic Semiconductor (Gallium (Paperback)

PMIn this dissertation, the ferromagnetic properties of the diluted magnetic semiconductor (Ga,Mn)As will be explored. The aim of this research is to characterize these properties using a wide variety of methods, then to explore their utility in the effect of exchange bias. We begin this dissertation by discussing the theoretical explanations as to why (Ga,Mn)As becomes ferromagnetic after the inclusion of Mn atoms into the GaAs lattice structure. Previous experiments detailing the work done in annealing will be explained, as well as the material properties of the dilute magnetic semiconductor. The dissertation will then deal with the magneto-optical Kerr effect (MOKE), an important tool in characterizing ferromagnetic materials. MOKE can be used to determine the Curie temperature of (Ga,Mn)As, and the experimental set-up for this will be shown. Once the case of generalized MOKE is explained, the dissertation will delve into a specific type of MOKE experiment, that of component-resolved MOKE. Component-resolved MOKE is an elegant experiment that can be particularly useful for materials undergoing a phase transition in magnetic anisotropy. It will be shown that tensile-strained (Ga,Mn)As undergoes such a transition, and the effect that annealing has on this transition will be demonstrated. The dissertation will then discuss the origin of the exchange bias effect, and how it relates to (Ga,Mn)As. Data will then be shown demonstrating that (Ga,Mn)As has been successfully exchange-biased, the first semiconductor to be done so. The various experiments exploring the chemical and structural properties of the MnO layer that exchange biases (Ga,Mn)As will be shown. Finally, the dissertation will finish with possible directions in which the MOKE and exchange bias experiments can be pursue