A adição de sais de lítio à líquidos iônicos gera mudanças em propriedades físicas relevantes, que comprometem sua possível aplicação em baterias de lítio, como aumento de viscosidade e redução da condutividade iônica. Possíveis causas para tais efeitos foram estudadas através da utilização de Espectroscopia Raman e Espectroscopia de Efeito Óptico Kerr. Foram estudadas as misturas dos liquídos iônicos: 1-butil-3metilimidazólio, N-(3- etóxietil)-N-metilmorfolínio e cátion 1-(3-etóxietil)-2,3-dimetilimidazólio possuindo em comum o contra-íon bis(trifluorometanosulfonil)imideto com diferentes concentrações de bis(trifluorometanosulfonil)imideto de lítio. O trabalho se dividiu em duas etapas principais, na primeira utilizou-se a espectroscopia Raman e observou-se o desdobramento da banda referente ao ânion em aproximadamente 740 cm-1, em dois diferentes picos, após a adição de lítio ao sistema. Esta observação forneceu indícios da ocorrência de mudanças estruturais possivelmente relacionadas a formação de agregados entre os ânions e o Li+. A partir destes resultados a obtenção de um valor aproximado para o número de coordenação médio dos cátions Li+ foi possível através da comparação da intensidade relativa dos dois picos para diferentes concentrações de sal. Foi ainda estudado o efeito da adição de água no sistema, causando o desaparecimento do pico Raman formado após a adição do sal de lítio, o que evidencia a capacidade da mesma de reduzir o efeito de agregação dos ânions ao redor do Li+. Na segunda etapa do trabalho, a técnica de espectroscopia de efeito óptico Kerr via detecção heterodina foi utilizada para a observação do perfil de relaxação orientacional nos sistemas descritos acima, a fim de examinar mudanças nos processos dinâmicos presentes após a adição sal inorgânico ao sistema. Os resultados foram analisados no contexto da teoria de acoplamento de modos, de maneira que utilizou-se um modelo fenomenológico desenvolvido através da observação de diferentes sistemas e da aplicação das equações propostas no modelo esquemático de Sjögren para a descrição da função de correlação polarizabilidade-polarizabilidade obtida pelo experimento. Os parâmetros encontrados demonstraram um alto grau de concordância com as observações estruturais observadas na primeira etapa, fornecendo evidências de que o lítio é capaz de afetar as estruturas locais presentes no líquido iônico puro de uma maneira similar ao efeito Chemla. O trabalho demonstrou que os mesmos princípios necessários para a síntese de líquidos iônicos a temperatura ambiente, primando a redução das interações atrativas entre os cátion e ânions para a estabilização da fase líquida, possui como efeito colateral o fato de que diversas moléculas apresentam interações mais fortes com seus íons alterando suas propriedades, neste caso prejudicando a utilização de líquidos iônicos como solventes alternativos em baterias de lítio. / The introduction of lithium salts to room temperature ionic liquids causes unwanted changes to the electrochemically relevant properties of these compounds, such as increase in viscosity and the reduction of ionic conductivity. Possible causes for these effects were studied with spectroscopic techniques such as Raman spectroscopy and Optical Kerr Effect spectroscopy. Mixtures of three different ionic liquids containing the cations: 1-butyl-3- methylimidazolium, N-(3-etoxyethyl)-N-methylmorfolinium and cátion 1-(3-etoxyethyl)-2,3- dimethylimidazolium and possessing the common counter ion bis(trifluoromethane sulfonyl)imide with lithium bis(trifluoromethane sulfonyl)imide. This work was divided in two parts, the first consisting of the use of Raman spectroscopy and the observation of the changes in the 740 cm-1 peak, pertaining to anion vibration after the introduction of lithium to the system, shown as the appearance of a new peak at higher frequencies. The approximate average lithium coordination number was determined by comparison of the relative intensities for different salt concentrations. The effect of water absorption in this system was also observed, showing that water molecules tend to hinder the formation of aggregates between the anion and Li+. The second step was carried out with the use of optically heterodyne detected optical Kerr effect spectroscopy to the analysis of the orientational relaxation profile for the systems described above. Results were analyzed through the application of Mode Coupling Theory models, both a phenomenological model obtained by the observation of different classes of liquids and the Mode Coupling Schematic model proposed by Sjögren were used to describe the polarizability-polarizabilty correlation function obtained from the experiments. The parameters obtained showed a high degree of correlation with the results obtained in the first part indicating that the introduction of a highly polarizing cation to the pure ionic liquid causes an effect similar to the Chemla effect observed in inorganic salt mixtures. The work showed evidences that the same principles used for the synthesis of room temperature ionic liquids, i.e. the reduction of attractive interactions between cation and anion or the addition of alkyl chains to reduce symmetry, result in various different compounds showing stronger interactions with the different ions resulting in changing properties, in this case hindering the use of ionic liquids as alternative green solvents for lithium ion batteries.

A adição de sais de lítio à líquidos iônicos gera mudanças em propriedades físicas relevantes, que comprometem sua possível aplicação em baterias de lítio, como aumento de viscosidade e redução da condutividade iônica. Possíveis causas para tais efeitos foram estudadas através da utilização de Espectroscopia Raman e Espectroscopia de Efeito Óptico Kerr. Foram estudadas as misturas dos liquídos iônicos: 1-butil-3metilimidazólio, N-(3- etóxietil)-N-metilmorfolínio e cátion 1-(3-etóxietil)-2,3-dimetilimidazólio possuindo em comum o contra-íon bis(trifluorometanosulfonil)imideto com diferentes concentrações de bis(trifluorometanosulfonil)imideto de lítio. O trabalho se dividiu em duas etapas principais, na primeira utilizou-se a espectroscopia Raman e observou-se o desdobramento da banda referente ao ânion em aproximadamente 740 cm-1, em dois diferentes picos, após a adição de lítio ao sistema. Esta observação forneceu indícios da ocorrência de mudanças estruturais possivelmente relacionadas a formação de agregados entre os ânions e o Li+. A partir destes resultados a obtenção de um valor aproximado para o número de coordenação médio dos cátions Li+ foi possível através da comparação da intensidade relativa dos dois picos para diferentes concentrações de sal. Foi ainda estudado o efeito da adição de água no sistema, causando o desaparecimento do pico Raman formado após a adição do sal de lítio, o que evidencia a capacidade da mesma de reduzir o efeito de agregação dos ânions ao redor do Li+. Na segunda etapa do trabalho, a técnica de espectroscopia de efeito óptico Kerr via detecção heterodina foi utilizada para a observação do perfil de relaxação orientacional nos sistemas descritos acima, a fim de examinar mudanças nos processos dinâmicos presentes após a adição sal inorgânico ao sistema. Os resultados foram analisados no contexto da teoria de acoplamento de modos, de maneira que utilizou-se um modelo fenomenológico desenvolvido através da observação de diferentes sistemas e da aplicação das equações propostas no modelo esquemático de Sjögren para a descrição da função de correlação polarizabilidade-polarizabilidade obtida pelo experimento. Os parâmetros encontrados demonstraram um alto grau de concordância com as observações estruturais observadas na primeira etapa, fornecendo evidências de que o lítio é capaz de afetar as estruturas locais presentes no líquido iônico puro de uma maneira similar ao efeito Chemla. O trabalho demonstrou que os mesmos princípios necessários para a síntese de líquidos iônicos a temperatura ambiente, primando a redução das interações atrativas entre os cátion e ânions para a estabilização da fase líquida, possui como efeito colateral o fato de que diversas moléculas apresentam interações mais fortes com seus íons alterando suas propriedades, neste caso prejudicando a utilização de líquidos iônicos como solventes alternativos em baterias de lítio. / The introduction of lithium salts to room temperature ionic liquids causes unwanted changes to the electrochemically relevant properties of these compounds, such as increase in viscosity and the reduction of ionic conductivity. Possible causes for these effects were studied with spectroscopic techniques such as Raman spectroscopy and Optical Kerr Effect spectroscopy. Mixtures of three different ionic liquids containing the cations: 1-butyl-3- methylimidazolium, N-(3-etoxyethyl)-N-methylmorfolinium and cátion 1-(3-etoxyethyl)-2,3- dimethylimidazolium and possessing the common counter ion bis(trifluoromethane sulfonyl)imide with lithium bis(trifluoromethane sulfonyl)imide. This work was divided in two parts, the first consisting of the use of Raman spectroscopy and the observation of the changes in the 740 cm-1 peak, pertaining to anion vibration after the introduction of lithium to the system, shown as the appearance of a new peak at higher frequencies. The approximate average lithium coordination number was determined by comparison of the relative intensities for different salt concentrations. The effect of water absorption in this system was also observed, showing that water molecules tend to hinder the formation of aggregates between the anion and Li+. The second step was carried out with the use of optically heterodyne detected optical Kerr effect spectroscopy to the analysis of the orientational relaxation profile for the systems described above. Results were analyzed through the application of Mode Coupling Theory models, both a phenomenological model obtained by the observation of different classes of liquids and the Mode Coupling Schematic model proposed by Sjögren were used to describe the polarizability-polarizabilty correlation function obtained from the experiments. The parameters obtained showed a high degree of correlation with the results obtained in the first part indicating that the introduction of a highly polarizing cation to the pure ionic liquid causes an effect similar to the Chemla effect observed in inorganic salt mixtures. The work showed evidences that the same principles used for the synthesis of room temperature ionic liquids, i.e. the reduction of attractive interactions between cation and anion or the addition of alkyl chains to reduce symmetry, result in various different compounds showing stronger interactions with the different ions resulting in changing properties, in this case hindering the use of ionic liquids as alternative green solvents for lithium ion batteries.

This thesis aims to explore the effect of in situ ion gun etching on magnetic proper- ties, such as perpendicular magnetic anisotropy, of Pt/Co/Pt multilayers. Perpendicular magnetic anisotropy is of interest due to its importance in spintronic application. Calibration spectroscopic ellipsometry measurements of Pt and Co layers to obtain sputter yields of respective magnetron targets were performed as a first step. After that, ten Pt/Co/Pt multilayers with different Co and top Pt layer thicknesses were prepared. Five of these samples were etched by the ion gun, mounted inside of the magnetron chamber, during different stages of the deposition. To characterize the prepared samples, experimental and modeled Kerr rotation spectra were confronted. This provided an insight into the cross-sections of the investigated samples. Magnetic hysteresis loops measured by vibrating sample magnetometer and Kerr rotation setup demonstrated higher coercive field and change of the slope of the loop induced by ion etching. When compared to the obtained cross-sections, a correlation between the change of magnetic loops and intermixing of Pt and Co at the interface was visible. This intermixing was higher in samples treated by the ion gun. 1

This thesis examines second-order optical nonlinear wave mixing processes in domain-disordered quasi-phase matching waveguides and evaluates their potential use in compact, monolithically integrated wavelength conversion devices. The devices are based on a GaAs/AlGaAs superlattice-core waveguide structure with an improved design over previous generations. Quantum-well intermixing by ion-implantation is used to create the quasi-phase matching gratings in which the nonlinear susceptibility is periodically suppressed. Photoluminescence experiments showed a large band gap energy blue shift around 70 nm after intermixing. Measured two-photon absorption coefficients showed a significant polarization dependence and suppression of up to 80% after intermixing. Similar polarization dependencies and suppression were observed in three-photon absorption and nonlinear refraction. Advanced modeling of second-harmonic generation showed reductions of over 50% in efficiency due to linear losses alone. Self-phase modulation was found to be the dominant parasitic nonlinear effect on the conversion efficiency, with reductions of over 60%. Simulations of group velocity mismatch showed modest reductions in efficiency of less than 10%. Experiments on second-harmonic generation showed improvements in efficiency over previous generations due to low linear loss and improved intermixing. The improvements permitted demonstration of continuous wave second-harmonic generation for the first time in such structures with output power exceeding 1 µW. Also, Type-II phase matching was demonstrated for the first time. Saturation was observed as the power was increased, which, as predicted, was the result of self-phase modulation when using 2 ps pulses. By using 20 ps pulses instead, saturation effects were avoided. Thermo-optically induced bistability was observed in continuous wave experiments. Difference frequency generation was demonstrated with wavelengths from the optical C-band being converted to the L- and U-bands with continuous waves. Conversion for Type-I phase matching was demonstrated over 20 nm with signal and idler wavelengths being separated by over 100 nm. Type-II phase matched conversion was also observed. Using the experimental data for analysis, self-pumped conversion devices were found to require external amplification to reach practical output powers. Threshold pump powers for optical parametric oscillators were calculated to be impractically large. Proposed improvements to the device design are predicted to allow more practical operation of integrated conversion devices based on quasi-phase matching superlattice waveguides.

Magneto-optical materials such as permalloy can be used to create artificial spin- ice (ASI) lattices with antiferromagnetic ordering. Magneto-optical materials used to create diffraction lattices are known to exhibit magnetic scattering at the half- order Bragg peak while in the ground state. The significant drawbacks of studying the magneto-optical generation of OAM using x-rays are cost, time, and access to proper equipment. In this work, it is shown that the possibility of studying OAM and magneto-optical materials in the spectrum of visible light at or around 2 eV is viable. Using spectroscopic ellipsometry it is possible to detect a change in the magnetization of thin permalloy films with thicknesses between 5 and 20 nm. Patterns consistent with OAM were found at 1.95 eV using a square lattice with a 4𝜋 radial phase shift in the antiferromagnetic ground state. Evidence of magnetic scattering at the half-order Bragg peak using 1.95 eV was also found.

This thesis examines second-order optical nonlinear wave mixing processes in domain-disordered quasi-phase matching waveguides and evaluates their potential use in compact, monolithically integrated wavelength conversion devices. The devices are based on a GaAs/AlGaAs superlattice-core waveguide structure with an improved design over previous generations. Quantum-well intermixing by ion-implantation is used to create the quasi-phase matching gratings in which the nonlinear susceptibility is periodically suppressed. Photoluminescence experiments showed a large band gap energy blue shift around 70 nm after intermixing. Measured two-photon absorption coefficients showed a significant polarization dependence and suppression of up to 80% after intermixing. Similar polarization dependencies and suppression were observed in three-photon absorption and nonlinear refraction. Advanced modeling of second-harmonic generation showed reductions of over 50% in efficiency due to linear losses alone. Self-phase modulation was found to be the dominant parasitic nonlinear effect on the conversion efficiency, with reductions of over 60%. Simulations of group velocity mismatch showed modest reductions in efficiency of less than 10%. Experiments on second-harmonic generation showed improvements in efficiency over previous generations due to low linear loss and improved intermixing. The improvements permitted demonstration of continuous wave second-harmonic generation for the first time in such structures with output power exceeding 1 µW. Also, Type-II phase matching was demonstrated for the first time. Saturation was observed as the power was increased, which, as predicted, was the result of self-phase modulation when using 2 ps pulses. By using 20 ps pulses instead, saturation effects were avoided. Thermo-optically induced bistability was observed in continuous wave experiments. Difference frequency generation was demonstrated with wavelengths from the optical C-band being converted to the L- and U-bands with continuous waves. Conversion for Type-I phase matching was demonstrated over 20 nm with signal and idler wavelengths being separated by over 100 nm. Type-II phase matched conversion was also observed. Using the experimental data for analysis, self-pumped conversion devices were found to require external amplification to reach practical output powers. Threshold pump powers for optical parametric oscillators were calculated to be impractically large. Proposed improvements to the device design are predicted to allow more practical operation of integrated conversion devices based on quasi-phase matching superlattice waveguides.

Title: Magnetic nanostructures for recording and optical sensors Author: Eva Lišková Department: Institute of Physics, Charles University Supervisor: Prof. Ing. Štefan Višňovský, DrSc. Abstract: Magneto-optical (MO) spectra of multilayered structures with enhanced MO effect were studied using the polar and longitudinal Kerr spectroscopy with oblique angle of light incidence in the photon energy range 1.2 eV to 5 eV. The samples with Fabry- Perot cavity like architecture, were modeled using Yeh matrix formalism. Two sets of samples, with composition FeF2/Fe/FeF2 and AlN/Fe/AlN, were prepared by molecular beam epitaxy and sputtering. The relations were studied between the position of the enhanced peak in the MO spectra and the structure. Second part of this work was devoted to the Pt/Co/Pt structures and the influence of the ion implantation on MO spectra and structural composition. The studied multilayer structures present interest for MO sensor and memory applications. Keywords: Magneto-optical Kerr effect, Magneto-optical sensor, Fabry-Perot resonator, Ion implantation

Made available in DSpace on 2014-12-17T15:14:57Z (GMT). No. of bitstreams: 1 EdimilsonFS_DISSERT.pdf: 2546760 bytes, checksum: 08525df56e96d75f8d221757342883b4 (MD5) Previous issue date: 2012-02-17 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work, we investigated the magnetic properties of a monocrystalline Fe thin film and of Fe(80 ?)/Cr(t)/Fe(80 ?) tri-layers, with the nonmagnetic metallic Cr spacer layer thickness varying between 9 ? < t < 40 ?. The samples were deposited by the DC Sputtering on Magnesium Oxide (MgO) substrates, with (100) crystal orientation. For this investigation, experimental magneto-optical Kerr effect (MOKE) magnetometry and ferromagnetic resonance (FMR) techniques were employeed. In this case, these techniques allowed us to study the static and dynamical magnetization properties of our tri-layers. The experimental results were interpreted based on the phenomenological model that takes into account the relevant energy terms to the magnetic free energy to describe the system behavior. In the case of the monocrystalline Fe film, we performed an analytical discussion on the magnetization curves and developed a numerical simulation based on the Stoner-Wohlfarth model, that enables the numerical adjustment of the experimental magnetization curves and obtainment of the anisotropy field values. On the other hand, for the tri-layers, we analyzed the existence of bilinear and biquadratic couplings between the magnetizations of adjacent ferromagnetic layers from measurements of magnetization curves. With the FMR fields and line width angular dependencies, information on the anisotropy in three layers was obtained and the effects of different magnetic relaxation mechanisms were evidenced. It was also possible to observe the dependence of the epitaxy of the multilayers with growth and sputtering parameters. Additionally it was developed the technique of AC magnetic susceptibility in order to obtain further information during the investigation of magnetic thin films / Nesta disserta??o investigamos as propriedades magn?ticas de um filme monocristalino de ferro e tricamadas com a composi??o Fe(80?)/Cr(t)/Fe(80?), variando as espessuras da camada met?lica n?o magn?tica separadora (Cr) entre 9? < t < 40?. As amostras foram depositadas pela t?cnica Sputtring DC sobre substrato de ?xido de Magn?sio (MgO) com orienta??o cristalina (100). Para esta investiga??o foram utilizadas as t?cnicas experimentais de magnetometria por efeito Kerr Magneto-?ptico (MOKE) e Resson?ncia Ferromagn?tica (FMR). Estas t?cnicas permitiram o estudo das propriedades est?ticas e din?micas da magnetiza??o das multicamadas. Os resultados experimentais foram interpretados com base no modelo fenomenol?gico que leva em considera??o os termos mais relevantes da energia livre magn?tica para descrever o comportamento do sistema. Para o filme monocristalino de ferro, realizamos uma discuss?o anal?tica das informa??es das curvas de magnetiza??o e desenvolvemos uma simula??o num?rica baseada no modelo de Stoner-Wohlfarth, possibilitando o ajuste num?rico das curvas de magnetiza??o experimentais e a obten??o do valor de campo de anisotropia. Para as tricamadas, analisamos a presen?a dos acoplamentos bilinear e biquadr?tico entre as magnetiza??es das camadas ferromagn?ticas adjacentes a partir das medidas das curvas de magnetiza??o. Com as depend?ncias angulares do campo de FMR e da largura de linha obtivemos informa??es sobre as anisotropias presentes nas tricamadas e evidenciamos os efeitos de diversos mecanismos de relaxa??o magn?tica. Tamb?m foi poss?vel observar a depend?ncia da epitaxia das multicamadas com os par?metros de crescimento do Sputtering. Adicionalmente foi desenvolvida, durante o per?odo do mestrado, a t?cnica de susceptibilidade magn?tica AC com o objetivo de obter resultados inovadores na investiga??o de filmes finos magn?ticos

Made available in DSpace on 2014-12-17T15:15:00Z (GMT). No. of bitstreams: 1 CharlieSG.pdf: 1382454 bytes, checksum: 2b54a2a0dcd81f1ca374af1328ff8c73 (MD5) Previous issue date: 2006-03-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / n this master s dissertation a Kerr Magneto Optic s magnetometer effect was set up to do characterization of samples type films fine and ultra thin, these samples will be grown after the implementation of the sputtering technique at the magnetism laboratory of of this department. In this work a cooled electromagnet was also built the water and that it reaches close values to 10kOe with a gap of 22 mm including an area of uniform field of 25mm of diameter. The first chapter treats of the construction of this electromagnet from its dimensioning to the operation tests that involve measures of reached maximum field and temperature of the reels when operated during one hour. The second chapter is dedicated to the revision of the magnetism and the magnetization processes as well as it presents a theoretical base regarding the magnetic energies found in films and magnetic multilayer. In the sequence, the third chapter, is especially dedicated the description of the effects magneto opticians the effect kerr in the longitudinal, traverse and polar configurations, using for so much only the classic approach of the electromagnetism and the coefficients of Fresnel. Distinguished the two areas of observation of the effect regarding thickness of the film. The constructive aspects of the experimental apparatus as well as the details of its operation are explained at the room surrender, also presenting the preliminary results of the measures made in one serializes of permalloy films and concluding with the results of the characterization of the first films of iron and permalloy grown here at the theoretical and experimental physics department at UFRN / Nesta disserta??o de mestrado foi montado um magnet?metro de efeito Kerr Magneto-?ptico para fazer caracteriza??o de amostras tipo filme fino e ultrafino, amostras estas que ser?o crescidas ap?s a implementa??o da t?cnica de Sputtering no laborat?rio de magnetismo deste departamento. Neste trabalho tamb?m foi constru?do um eletro?m? arrefecido a ?gua e que atinge valores pr?ximos a 10 kOe com um gap de 22 mm abrangendo uma regi?o de campo uniforme de 25 mm de di?metro. O primeiro cap?tulo trata da constru??o deste eletro?m? desde o seu dimensionamento at? os testes de opera??o que envolvem medidas de campo m?ximo alcan?ado e temperatura das bobinas quando operando durante 1 hora. O capitulo 2 ? dedicado a uma revis?o do magnetismo e dos processos de magnetiza??o bem como apresenta uma base te?rica a respeito das energias magn?ticas encontradas em filmes e multicamadas magn?ticas. Na seq??ncia, o terceiro cap?tulo, ? dedicado a descri??o dos efeitos magneto ?pticos em especial o efeito kerr nas configura??es longitudinal, transversal e polar, utilizando para tanto somente a abordagem cl?ssica do eletromagnetismo e os coeficientes de Fresnel. Distinguindo em seguida, as duas regi?es de observa??o do efeito referentes a espessura do filme. Os aspectos construtivos do aparato experimental bem como os detalhes de sua opera??o s?o explanados no quarto capitulo, apresentando tamb?m os resultados preliminares das medidas efetuadas em uma serie de filmes de Permalloy e finalizando com os resultados da caracteriza??o dos primeiros filmes de ferro e Permalloy crescidos aqui no departamento de f?sica te?rica e experimental da UFRN

Orientador: Munir Salomão Skaf / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-05T22:46:02Z (GMT). No. of bitstreams: 1 Sonoda_MiltonTaidi_D.pdf: 3606314 bytes, checksum: dd30d5b14e2acb05e75ed7277f70cead (MD5) Previous issue date: 2005 / Doutorado / Físico-Química / Doutor em Ciências