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Magneto-optic response of layered media
Kunt, Ota ; Ostatnický, Tomáš (advisor) ; Antoš, Roman (referee)
Optical response of materials strongly depends on their magnetic properties. This phenomenon is also used in materials in the form of thin layers and multi- layers. Using cited literature we summarize theory needed to calculate magneto- optical response of multilayers. The calculation is based on Maxwell equations and magnetic materials are described with effective permittivity tensor. Jones formalism is used to describe polarised light and Yeh formalism is used to de- scribe multilayer response. A program using presented theory was developed and calculations for concrete structure were made. Multilayer parameters were cho- sen to correspond with those of a sample whose magneto-optical response was measured at the Department of Chemical Physics and Optics, MFF UK. 1
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Rigorous electromagnetic theory of the optical response of periodic nanostructures
Navrátil, Josef ; Antoš, Roman (advisor) ; Richter, Ivan (referee)
The diffraction of light is an important phenomenon with wide physical and engineering appli- cations and diffraction gratings are optical components with a periodic structure which are used to diffract light into several beams propagating in various directions. Direct methods like AFM or SEM proved to be insufficient to study the shape of planar diffraction gratings and therefore they must be supplemented with results obtained from optical spectroscopy. Computer simulations are the integral part of this method. This Thesis is focused on two particular simulation methods - the RCWA and the C-Method. It gives a rich theoretical introduction, discusses the weaknesses of these methods and also describes improvements of the RCWA using the Airy-like series and proper Fourier factorization. Both methods are implemented, tested on simple examples and af- terwards the convergence for particular cases is investigated. The C-Method and the modified RCWA algorithm exhibit excellent convergence. At the end, the numeric results are compared with experiments, giving a very good agreement in the ellipsometric parameters. 1
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Investigation of magnetization dynamics in GaMnAs by ultrafast laser spectroscopy
Tesařová, Naďa ; Němec, Petr (advisor) ; Ferguson, Andrew (referee) ; Antoš, Roman (referee)
i Abstract: This doctoral thesis is dedicated to the study of magnetization dynamics in ferromagnetic semiconductor (Ga,Mn)As using magneto-optical (MO) spectroscopy methods. The character of the magnetization dynamics after the impact of the laser pulse was investigated under different experimental conditions in an extensive set of optimized (Ga,Mn)As samples with Mn doping ranging from 1.5% to 14%. The thorough analysis of the measured MO signal enabled us to develop a new method that can be used to determine the laser pulse-induced real-space magnetization trajectory without any numerical modelling. Moreover, the investigation of the measured MO signals allowed us to determine the basic micromagnetic properties of (Ga,Mn)As, such as the magnetic anisotropy, the Gilbert damping or the spin stiffness. In addition to this, we found out that the light-induced magnetization precession can be caused by three distinct mechanisms - the sample heating due to the energy transfer from the laser pulses, the angular momentum transfer from the circularly polarized photons, and the influence of the non-equilibrium hole polarization induced by the relativistic spin-orbit interaction. The first of these mechanisms is rather well known but the two remaining ones, which are the optical analogues of the spin-transfer torque...
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Study of ferrimagnetic garnets thin films for photonic applications
Tázlarů, Stáňa ; Veis, Martin (advisor) ; Antoš, Roman (referee)
The aim of this thesis was an optical and magneto-optical characterization of thin layers of iron garnets prepared on silicon substrate by pulsed laser deposition method with emphasis on determining their suitability for use as materials for integrated optical isolators. The work is primarily dedicated to study of a single-layer terbium iron garnet samples and the influence of bismuth and cerium substitutions on their properties. Pre- sented values of a quality parameter, the figure of merit, are comparable with previously published results of two-layer structures of yttrium iron garnets and up to an order of magnitude higher than other available published values in this field. 1
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Optical and magneto-optical spectroscopies of thin NiMnGa films with martensitic transformation
Makeš, Matěj ; Veis, Martin (advisor) ; Antoš, Roman (referee)
In this thesis we provide a systematic study of optical and magneto-optical properties of thin NiMnGa films - alloys exhibiting magnetic shape memory effect. These layers were prepared by magnetron sputtering. A series of samples with different deposition temperatures, different thicknesses, different stoichiometries and different substrates were measured. The analysis of the obtained results clearly demonstrated the influence of change in strain, which is induced by the substrate, with varying thickness. Also the influence of stoichiometry on the amplitude of the magneto-optical Kerr effect and the influence of the base layer on the structure of the Ni-Mn-Ga layer were demonstrated. 1
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Epitaxial films of ceria for opto- electronics
Kubát, Jan ; Mysliveček, Josef (advisor) ; Antoš, Roman (referee)
This diploma thesis studies magneto-optical (MO) response of epitaxial thin films of Co-doped ceria. Thin films were characterized by XPS, LEED, STM, spectroscopic ellipsometry and measurement of MO activity. The work focuses on studying MO response of the films depending on film thickness, cobalt concentration, oxidation state of cerium and chemical state of cobalt. Spectra of MO response consist of low energy region where the MO activity is mediated by transitions from defect induced states to conduction band and high energy region where a peak of MO activity appears which we attribute to transitions from valence band to conduction band. In this work we qualitatively explain the effects of the physico- chemical states of the thin films on the structure of the obtained MO spectra, mainly on the appearance of the MO activity in the low energy region, and on the changes of the position of the MO peak. Compared to other preparation methods the epitaxial thin films allow achieving a shift of the MO peak in the direction of higher photon energy.
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Epitaxial films of ceria for opto- electronics
Kubát, Jan ; Mysliveček, Josef (advisor) ; Antoš, Roman (referee)
This diploma thesis studies magneto-optical (MO) response of epitaxial thin films of Co-doped ceria. Thin films were characterized by XPS, LEED, STM, spectroscopic ellipsometry and measurement of MO activity. The work focuses on studying MO response of the films depending on film thickness, cobalt concentration, oxidation state of cerium and chemical state of cobalt. Spectra of MO response consist of low energy region where the MO activity is mediated by transitions from defect induced states to conduction band and high energy region where a peak of MO activity appears which we attribute to transitions from valence band to conduction band. In this work we qualitatively explain the effects of the physico- chemical states of the thin films on the structure of the obtained MO spectra, mainly on the appearance of the MO activity in the low energy region, and on the changes of the position of the MO peak. Compared to other preparation methods the epitaxial thin films allow achieving a shift of the MO peak in the direction of higher photon energy.
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Study of ferrimagnetic garnets thin films for photonic applications
Tázlarů, Stáňa ; Veis, Martin (advisor) ; Antoš, Roman (referee)
The aim of this thesis was an optical and magneto-optical characterization of thin layers of iron garnets prepared on silicon substrate by pulsed laser deposition method with emphasis on determining their suitability for use as materials for integrated optical isolators. The work is primarily dedicated to study of a single-layer terbium iron garnet samples and the influence of bismuth and cerium substitutions on their properties. Pre- sented values of a quality parameter, the figure of merit, are comparable with previously published results of two-layer structures of yttrium iron garnets and up to an order of magnitude higher than other available published values in this field. 1
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