Thesis (Ph.D.)--York University, 2005. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 231-232). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNR11640

Three applications of Smith's model of magneto-optical effects in stratified magnetic media are presented. Each application involves the incident-angle dependence of magneto-optical effects which Smith's model treats explicitly. In addition. the three applications address current issues in magnetic and magneto-optical recording. The first problem considered is that of nonmagnetic surface layers which form on magnetic recording heads. The second is a theoretical treatment of effects which arise in magneto-optical recording when high numerical-aperture optical systems are combined with media exhibiting interference-enhanced optical properties. The final application is a novel technique for determining the entire dielectric tensor of materials used for magneto-optical recording. The incident-angle dependence of the longitudinal Kerr effect is employed to study nonmagnetic surface layers which form on ferrite recording heads. Calculations based on the Smith model show a correlation between the inert-layer thickness and the incident-angle dependence of the longitudinal Kerr effect. Experimental results confirm the shift in the angular position of the signal peak. in agreement with the theory for finite inert-layer thickness. An unambiguous determination of the inert-layer thickness for ferrite materials is prevented because of a periodic dependence of the peak angle on the inert-layer thickness. Jones-matrix algebra is used with the Smith model to quantitatively determine the effects of obliquely-incident rays on the reflectance and magneto-optical readout signals for various magneto-optical media structures. The most antireflective structure is found to be very sensitive to incident-angle effects. Structures with moderate reflectance (>10%). however. are not significantly affected by incident-angle effects. Finally. a technique for the determination of the optical and magneto-optical constants from multiple incident-angle measurements of reflectance and Kerr rotation is presented. The experimental system employs a Helium-Neon laser and a rotating differential detection system. The technique is used to investigate the optical properties of a series of Cu/Co multilayers and a comparison with a model based on the bulk optical. constants of Cu and Co is made. Anomalous behavior is observed for multilayers with very thin periods.

Short resumés of the theories of propagation of electromagnetic waves in an anisotropic medium, of the Faraday effect, and of the influence of paramagnetic resonance on the Faraday effect are given. The Poincaré sphere is introduced to describe polarized light. A paramagnetic resonance spectrometer is described, which was modified so as to allow the study of magneto-optical phenomena under the influence of paramagnetic resonance. The spectrometer operated in the X-band using a 2K39 Klystron. The samples were located in a transmission type cavity operating in the TE 101 mode, and immersed in liquid helium. The cavity was provided with holes allowing the passage of light through the sample in a direction parallel to the external magnetic field. An optical system provided plane-polarized monochromatic light ( ג = 5461 Å ) incident on the sample. The light emerging from the sample passed through a Glan-Thompson prism analyzer. The relative intensity of the light passing the analyzer could be measured by a photomultiplier circuit and could be displayed as a function of time on an oscilloscope. Experiments are described in detail in which the spin-lattice relaxation time was measured as a function of temperature and external magnetic field. In these experiments, for a given temperature and magnetic field, the Faraday rotation was reduced by pulses of microwave power of varying length applied to the cavity. The return of the Faraday rotation as a function of time to its equilibrium value after the microwave power was cut off could be inferred from the intensity versus time relationship of the light transmitted by the analyzer. Photographic records of this intensity versus time relationship were obtained and the relaxation time was deduced from these records. Results of the measurement of the spin-lattice relaxation time of neodymium ethylsulfate for fields between 780 and 2540 Oerstedt and temperatures between 1.38°K and 4.22°K are given. The relaxation times measured were of the order of .001 to .1 seconds. The relaxation time appeared to be inversely proportional to the third power of the temperature and showed only small field dependence, except for a large dip at a field corresponding to the resonance field for the microwave frequencies used. Within the accuracy of the experiments no effect of the length of the microwave pulses on the relaxation time could be observed. An experiment on cerium ethylsulfate is described, which showed that the spin-lattice relaxation time must be smaller than 1 millisecond for this salt. No accurate determination of the relaxation time could be made in this case. Mention is made of an "overshoot effect" observed in one particular crystal of neodymium ethylsulfate. A possible explanation for this effect is given, by assuming that the crystal in question was twinned. In this case one may infer that the relaxation time is strongly dependent on the orientation of the optical axis of the crystal with respect to the external magnetic field The results were found to disagree with present-day theories of paramagnetic relaxation. Assumptions of doubtful validity in the theory are discussed as possible reasons for such disagreement. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The goal of the thesis is to make contributions to the development of two new technologies for data storage: perpendicular recording and magneto-optic recording. CoCr and rare earth-transition metal multilayers are the most suitable media for perpendicular recording and magneto-optic recording technologies, respectively. In part A of the thesis, magnetic properties of CoCr thin films produced by dc magnetron sputtering are studied for various deposition conditions. Dielectric constants and extraordinary Hall effect are also studied to provide information complementary to magnetic properties. In part B, new methods are developed for theoretical analysis of the magneto-optics of rare earth-transition metal multilayers, which can be used to optimize the readout of the recording system. Part A For dc magnetron sputtered CoCr films the perpendicular and parallel magnetic coercivities are found to be mainly controlled by the substrate temperature during film growth. Substrate temperatures between 180 and 300 C are necessary to fabricate CoCr thin films for recording media. Films produced in this manner have magnetic anisotropy constants ranging from —1.0 to +0.5 10⁶erg/cc. The magnetic anisotropy has a complicated dependence on a large number of deposition parameters and can be best controlled by the dc sputtering power and the target-to-substrate distance. Based on microstructural analysis film properties are interpreted in terms of the adatom diffusion during film growth. It is found that high adatom mobility and low deposition rate promote positive magnetic anisotropy. The dielectric constants measured by ellipsometry are found to depend on the film thickness because of the change in film morphology during film growth. The effects of asymmetric sputtering are analyzed, and the relationship between the extraordinary Hall effect and the magnetic properties is investigated. Part B The 4x4 matrix method proposed by Lin-Chung and Teitler[P. J. Lin-Chung and S. Teitler, J. Opt. Soc. Am. A 1 703(1984)] is applied to the magneto-optics of the rare earth-transition metal multilayer system. Based on a plane wave model, the above method enables one to calculate the sensitivity of the readout to the layer thicknesses as well as effects of oblique angle of incidence, anisotropy in the nonmagnetic part of the dielectric constants and misalignment of the magnetization. Finally, an improved model is presented to take into account the fact that the reading laser is a strongly focused beam instead of a plane wave. This new model is used to optimize the magneto-optic multilayer system. When the focal spot size of the reading laser beam is less than about three wavelengths, significantly different results are obtained from the focused beam and the plane wave models. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Francis Bitter. / "March 16, 1955." / Bibliography: p. 20. / Army Signal Corps Contract DA36-039 sc-42607 Project 132B Dept. of the Army Project 3-99-12-022

J.R. Eshbach [and] M.W.P. Strandberg. / "February 4, 1952." / Bibliography: p. 12. / Army Signal Corps Contract No. DA36-039 sc-100 Project No. 8-102B-0. Dept. of the Army Project No. 3-99-10-022.

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Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Highly sensitive magneto-optical techniques have been used to investigate weak linear and nonlinear optical absorption mechanisms in p- and n-type InSb. As a result, new absorption processes involving both impurities and free carriers have been identified and studied in detail. For p-InSb, magneto-optical spectra has been obtained over a wide range of temperatures and photon energies. The spectra obtained at higher sample temperatures are seen to result from combined-resonance transitions of free holes between heavy-and light-hole Landau levels, while bound-hole transitions between ground heavy-hole-like and excited light-hole-like acceptor states are observed at lower temperatures. Analysis of the combined-resonance data along with extensive intra-conduction band and two-photon interband data using a modified Pidgeon and Brown 8X8 energy band model has allowed the determination of a single set of band parameters for InSb that quantitatively describes these different sets of data. In addition, a ground state binding energy of 8.1 meV for Cd acceptors and 42.5 meV for Au acceptors has been extracted from the analysis of the bound-hole spectra. For n-lnSb, photo-Hall techniques have been developed and used to study both resonant impurity and two-photon magneto-absorption (TPMA) processes in detail. As a result, LO-phonon-assisted impurity cyclotron resonance harmonic (LOICRH) transitions from the shallow Te donor level have been observed for the first time. In addition, transitions from deep levels are also observed in the photo-Hall signal obtained at sample temperatures greater than 20K. Both time-resolved and intensity-dependent measurements on impurity and TPMA processes are reported and the results compared directly with the predictions of rate equations describing the photoexcited carrier dynamics. These investigations have yielded important information about the optical properties of n-InSb; e.g. impurity and two-photon absorption coefficients, photo-excited carrier lifetimes, and recombination rates.