Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 165-179. Includes list of publications: leaf 180-181.

Os calcógenos de európio (EuX, onde X representa O, S, Se ou Te) possuem propriedades magneto-ópticas únicas e interessantes, devido ao enorme magnetismo gerado dos elétrons na camada f do átomo pertencente a família dos terras raras, tornando estes materiais atraentes para aplicações na spintrônica (eletrônica baseada nos transporte de spins e não de carga). Neste trabalho investigamos em baixa temperatura o espectro de absorção utilizando luz circularmente polarizada na região próxima do limiar da banda para o telureto de európio EuTe e o seleneto de európio EuSe em alto campo magnético no ordenamento ferromagnético dos spins de Eu^{2+} da rede cristalina. As amostras crescidas por epitaxia por feixe molecular apresentaram um dicroísmo circular magnético intenso no espectro de absorção para a configuração de Faraday. O par de linhas estreitas observadas estão separadas de aproximadamente 200 meV para o EuTe e 300 meV para o EuSe. Em seguida, formulamos um modelo teórico para a interpretação deste espectro de absorção no arcabouço do modelo de transições eletrônicas entre o estado fundamental 4f^{7}({8}^S_{7/2}) e o estado excitado formado dos estados do caroço remanescente 4f^{6}({7}^F_{J=0...6}) mais o estado em que o elétron se encontra na banda de condução 5d(t_{2g}), resultando em uma excelente concordancia qualitativa e quantitativa com o experimento. / Europium chalcogenides (EuX, where X stands for O, S, Se or Te) have very interesting and unique magneto-optical properties, due to the huge magnetism that arises from the electrons in the f?shell of the rare earth element and which makes them attractive for spintronics applications ( spin transport electronics or spin basedelectronics) In this work we investigate the band-edge optical absorption in high magnetic fields in the Faraday geometry for EuTe and EuSe in the ferromagnetic order attained at low temperatures. In thin layers grown by molecular beam epitaxy, an intense magnetic circular dichroism were observed. The doublet of absorption lines showed a separation by about 200meV in EuTe and 300meV in EuSe. Next, we developed a theoretical model for the interpretation of the absorption spectrum, based in the framework of the model of an electronic transition from a localized ground state 4f^{7}({8}^S_{7/2)) to an excited state formed by the core states 4f^{6}({7}^F_{J=0...6}) and the electron extended state in the 5d(t_{2g}) conduction band, yielding an excellent qualitative and quantitavie agreement with experiment.

The primary goal of my dissertation was to build a Scanning Hall Probe Microscope (SHPM) for studying the domain structure of a ferromagnetic semiconductor (Ga[subscript 0.94]Mn[subscript 0.06]). This new semiconductor may be used in the emerging field of spintronics, where both the charge and spin of an electron are utilized. The first part of this dissertation introduces the scanning probe microscopy techniques that are used for our homemade SHPM performance test and images. In chapter 2, general spintronics and ferromagnetic semiconductor are introduced. A compact design of our LT-SHPM is introduced in chapter 3. A unique taper seal based on stainless steel and Cu for opening/closing the vacuum chamber is used for our homemade SHPM. In chapter 4, Hall probes are discussed. In this chapter, ESD (Electrostatic discharge) and its repair work are discussed. Finally, in Chapter 5, SHPM imaging results of Ga[subscript 0.94]Mn[subscript 0.06]As are discussed. We observed stripe domain patterns. We also observed the domain patterns as a function of magnetic field and temperature. / text

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Thesis (Ph.D.)--Tufts University, 1989. / Submitted to the Dept. of Physics. Includes bibliographical references (leaves 192-204). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--Tufts University, 1998 . / Adviser: Yaacov Shapira. Submitted to the Dept. of Physics. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D., Material Sciences and Engineering)--University of Idaho, January 2008. / Major professor: Keith A. Prisbrey. Includes bibliographical references (leaves 85-90). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Includes bibliographical references (leaves 122-126). Issued in print and online. Available via ProQuest Digital Dissertations.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 194-209).