O presente trabalho realiza a investigação de interações hiperfinas em amostras de óxido de zinco dopado com metais de transição por meio da técnica de Correlação Angular γ - γ Perturbada (CAP), baseada em interações hiperfinas. Para a realização das medidas, utilizou-se núcleos de prova radioativos de 111In -> 111 Cd que decaem através da cascata gama 171-245keV com nível intermediário de 245keV (I = 5+/2, Q = 0.83b, T1/2 = 84.5ns). Inicialmente, amostras de óxido de zinco dopadas com diferentes metais de transição foram confeccionadas por meio de um processo sol-gel para a obtenção de amostras óxidas. Realizou-se, então, o processo de caracterização destas amostras por meio de diferentes técnicas (Difração de Raios-X, Microscopia Eletrônica de Varredeura e Espectroscopia EDS) onde se sucedeu a investigação de interações hiperfinas (por meio da técnica CAP) a fim de se obter maior compreensão a respeito das interações quadrupolares elétricas presentes nas amostras, bem como a possibilidade da existência de comportamento ferromagnético à temperatura ambiente, aspecto este que vem sendo intensamente investigado, e que é de elevado interesse no que diz repeito à futuras aplicações. Os resultados obtidos foram analisados e discutidos em face dos modelos e das informações encontradas na literatura. As discussões foram realizadas em função das diferentes temperaturas de medida, tratamentos térmicos, tamanho das partículas, tipo e concentração de elementos dopantes, possibilitando uma discussão detalhada bem como a interpretação física dos resultados obtidos, apresentando-se as respectivas conclusões. / In the present work, a microscopic investigation of hyperfine interactions in zinc oxide samples doped with transition metals was carried out by means of Perturbed Angular γ γ Correlation technique (PAC), which is based on hyperfine interactions. This technique makes use of 111In -> 111 Cd radioactive probe nuclei, which decay through the well known cascade 171-245keV with an intermediate level of 245keV (I = 5+/2 ,Q = 0.83b, T1/2 = 84.5ns). First, zinc oxide samples doped with different transition metals were obtained by means of a sol-gel method for production of oxide samples. Then, samples were characterized by means of different techniques (X-Ray Difraction, Scanning Electronic Microscopy and Energy Dispersive Spectroscopy), followed by the investigation of hyperfine interactions (using PAC technique), in order to increase the understanding concerning electric quadrupole interactions in these samples, as well as the possibility of obtaining ferromagnetic behavior at room temperature, which has been extensively investigated and is an aspect of high interest concerning future applications. Results obtained from measurements were analyzed and compared with the information found in literature. Discussions were made as function of different measurement temperatures, annealing procedures, particle size, type and concentration of doping elements, making possible to produce a detailed discussion as well as the physical interpretation of the results obtained, presenting the respective conclusions.

Neste trabalho foi realizado um estudo sistemático, das interações hiperfinas (campo hiperfino magnético e campo hiperfino elétrico), nos compostos do tipo RMn2Si2 e RMn2Ge2 (onde R = La, Nd, Pr), sendo que, para a amostra de La foi estudada a série LaMn2(Si(1-x)Gex)2 (onde x = 0, 0.2, 0.4, 0.6, 0.8, 1), por meio da técnica de correlação angular gama-gama perturbada (CAP), utilizando os núcleos de prova 111In(111Cd) e 140La(140Ce). Além disso, foram realizadas medições para a caracterização estrutural utilizando a técnica de difração de raios X, para a caracterização magnética, a nível macroscópico, através de medições de magnetização, caracterização nuclear utilizando a técnica de espectrometria da radiação gama e um estudo complementar por cálculos de primeiros princípios somente para as amostras de LaMn2Ge2 e LaMn2Si2. A maior contribuição para o comportamento magnético nesses compostos tem origem no ordenamento magnético da sub rede do Mn, que aparece em temperaturas relativamente altas, da ordem de 480 K, sendo que, esses compostos possuem um ordenamento antiferromagnético e próximo a temperatura ambiente passam a possuir um ordenamento ferromagnético. Além disso, para o caso especifico dos compostos PrMn2Ge2 e NdMn2Ge2, abaixo de 40K é observado, também, o ordenamento ferromagnético dos spins da sub rede da terra rara. O núcleo de prova 111In(111Cd) foi utilizado para medir, tanto as interações de quadrupolo elétrico, como de dipolo magnético na rede do Mn (interação matrizmatriz). Esses resultados evidenciaram a transição de fase magnética (antiferromagnética para ferromagnética), sendo que, o campo hiperfino magnético, para as duas fases magnéticas, segue o comportamento da função de Brillouin. Já o núcleo de prova 140La(140Ce) permitiu medir a interação de dipolo magnético, tanto originada pela rede do Mn, como pela rede da terra rara. Mas, nesse caso, pode ser verificado somente o campo hiperfino magnético da fase ferromagnética da rede do Mn. Para a análise dos resultados PAC levou-se em conta uma interação matriz-impureza, pois o íon Ce3+ possui um elétron 4f desemparelhado, que pode contribuir para o campo hiperfino total. O composto LaMn2Si2 apresentou o comportamento do campo hiperfino magnético com a temperatura que segue o comportamento da função de Brillouin. Já os compostos LaMn2Ge2, PrMn2Ge2 e NdMn2Ge2 apresentaram um comportamento anômalo ao da função de Brillouin. Esse comportamento pode ser associado a uma forte hibridização da banda 4f do Ce com a banda 3d do Mn, tal conclusão foi reforçada pelos resultados do DOS (densidade de estados), resultados dos cálculos de primeiros princípios, dos compostos LaMn2Si2 e LaMn2Ge2. / This thesis reports a systematic study of the hyperfine interactions (magnetic hyperfine field and electric field gradient) in the RMn2Si2 and RMn2Ge2 ( R = La, Nd, Pr) compounds as well as in LaMn2(Si(1-x)Gex)2 (where x = 0, 0.2, 0.4, 0.6, 0.8, 1) mixed compounds. The hyperfine interactions were measured through Perturbed Angular Correlation Gamma-Gamma Spectroscopy technique using 111In(111Cd) and 140La(140Ce) as probe nuclei. Structural, magnetic and chemical analysis characterization were carried out by X-ray diffraction, magnetization measurements and gamma radiation spectrometry, respectively. An additional study by first-principles calculations for LaMn2Ge2 e LaMn2Si2 samples were also performed. The magnetic behavior in these compounds is mainly associated with the ordering of the magnetic moments of Mn sublattice, which appears at high temperature around 480 K. All studied compounds undergo a transition from antiferromagnetic to ferromagnetic ordering around room temperature. Specifically for PrMn2Ge2 and NdMn2Ge2 compounds, an additional ferromagnetic ordering due to the polarization of Pr or Nd magnetic moments is also observed below 40 K. 111In(111Cd) probe nuclei were used to measure the temperature dependence of the electric quadrupole and the dipole magnetic interactions at the Mn sublattice (matrix-matrix interaction). The results show the magnetic transition (antiferromagnetic to ferromagnetic phase), where the magnetic hyperfine field associated to both magnetic phases follows the Brillouin function. For the 140La(140Ce) probe nuclei, only dipole magnetic interaction measurements in the ferromagnetic phase were possible, also caused by the Mn sublattice and, for R = Pr, Nd, by the rare earth sublattice. The analysis of results considers a matrix-impurity interaction because the Ce3+ has an unpaired 4f electron, which can contribute to the total hyperfine field. The compound LaMn2Si2 presents a behavior for the temperature dependence of the magnetic hyperfine field that could be fitted by a Brillouin function. On the other hand, LaMn2Ge2, PrMn2Ge2 and NdMn2Ge2 compounds showed an anomalous Brillouin function behavior. This behavior can be associated with a strong hybridization Ce 4f band with the Mn 3d band. Such conclusion was reinforced by the DOS (density of stats), first-principles calculations, results to LaMn2Si2 and LaMn2Ge2.

O presente trabalho realiza a investigação de interações hiperfinas em amostras de óxido de zinco dopado com metais de transição por meio da técnica de Correlação Angular γ - γ Perturbada (CAP), baseada em interações hiperfinas. Para a realização das medidas, utilizou-se núcleos de prova radioativos de 111In -> 111 Cd que decaem através da cascata gama 171-245keV com nível intermediário de 245keV (I = 5+/2, Q = 0.83b, T1/2 = 84.5ns). Inicialmente, amostras de óxido de zinco dopadas com diferentes metais de transição foram confeccionadas por meio de um processo sol-gel para a obtenção de amostras óxidas. Realizou-se, então, o processo de caracterização destas amostras por meio de diferentes técnicas (Difração de Raios-X, Microscopia Eletrônica de Varredeura e Espectroscopia EDS) onde se sucedeu a investigação de interações hiperfinas (por meio da técnica CAP) a fim de se obter maior compreensão a respeito das interações quadrupolares elétricas presentes nas amostras, bem como a possibilidade da existência de comportamento ferromagnético à temperatura ambiente, aspecto este que vem sendo intensamente investigado, e que é de elevado interesse no que diz repeito à futuras aplicações. Os resultados obtidos foram analisados e discutidos em face dos modelos e das informações encontradas na literatura. As discussões foram realizadas em função das diferentes temperaturas de medida, tratamentos térmicos, tamanho das partículas, tipo e concentração de elementos dopantes, possibilitando uma discussão detalhada bem como a interpretação física dos resultados obtidos, apresentando-se as respectivas conclusões. / In the present work, a microscopic investigation of hyperfine interactions in zinc oxide samples doped with transition metals was carried out by means of Perturbed Angular γ γ Correlation technique (PAC), which is based on hyperfine interactions. This technique makes use of 111In -> 111 Cd radioactive probe nuclei, which decay through the well known cascade 171-245keV with an intermediate level of 245keV (I = 5+/2 ,Q = 0.83b, T1/2 = 84.5ns). First, zinc oxide samples doped with different transition metals were obtained by means of a sol-gel method for production of oxide samples. Then, samples were characterized by means of different techniques (X-Ray Difraction, Scanning Electronic Microscopy and Energy Dispersive Spectroscopy), followed by the investigation of hyperfine interactions (using PAC technique), in order to increase the understanding concerning electric quadrupole interactions in these samples, as well as the possibility of obtaining ferromagnetic behavior at room temperature, which has been extensively investigated and is an aspect of high interest concerning future applications. Results obtained from measurements were analyzed and compared with the information found in literature. Discussions were made as function of different measurement temperatures, annealing procedures, particle size, type and concentration of doping elements, making possible to produce a detailed discussion as well as the physical interpretation of the results obtained, presenting the respective conclusions.

No presente trabalho, a técnica de Espectroscopia de Correlação Angular Perturbada (CAP) foi usada para medir a interação de quadrupolo elétrico em amostras de DNA de diferentes linhagens de camundongos (A/J, C57BL/6, B6AF1, BXA1 e BXA2), amostras de antiimunoglobulinas pertencentes as subclasses (IgG1, IgG2a e IgG2b) e de porções ativas de imunoglobulinas fracionadas ou inteiras, correspondentes a parte diversificada da imunoglobulina, responsável pelo padrão de resposta imunológica apresentado pelos organismos. Também foram realizadas medidas da interação de quadrupolo elétrico em amostras de bases nitrogenadas do DNA (adenina, citosina, guanina e timina). As medidas CAP foram realizadas utilizando os núcleos de prova 111In111Cd; 111mCd111Cd; 111Ag111Cd; e 181Hf181Ta, nas temperaturas ambiente e do nitrogênio líquido para investigar as interações dinâmicas e estáticas, respectivamente. As biomoléculas foram marcadas por meio direto, onde os átomos dos núcleos de prova devem se ligar a um determinado sítio da biomolécula. Os materiais biológicos e os núcleos de prova foram escolhidos com o objetivo de verificar, em todos os seus aspectos, a possibilidade de aplicação da espectroscopia de CAP na investigação dos parâmetros hiperfinos em um núcleo de prova de um átomo metálico ligado às biomoléculas (incluindo o uso de diferentes núcleos de prova, resultantes do decaimento do núcleo pai de quatro diferentes metais) e estudar, por meio dos parâmetros hiperfinos medidos, o comportamento dessas diferentes moléculas. Os resultados obtidos mostram as diferenças entre a interação das biomoléculas estudadas com os núcleos de prova Estas diferenças foram observadas por meio de variações nos parâmetros hiperfinos medidos, que depende do tipo de molécula, mostrando que o núcleo de prova em alguns casos ligou-se as moléculas e em outros não houve esta ligação. / In the present work perturbed angular correlation (PAC) spectroscopy was used to measured electric quadrupole interactions in DNA biomolecules of different mice lineages (A/J, C57BL/6, B6AF1, BXA1 e BXA2), samples of different isotypes of immunoglobulin G (IgG1, IgG2a e IgG2b) and active portions of complete and fragmented immunoglobulin responsible by the immune response. Electric quadrupole interactions were also measured in DNA nitrogenous bases (adenine, cytosine, guanine, thymine). PAC measurements were performed using 111In111Cd; 111mCd111Cd; 111Ag111Cd; e 181Hf181Ta as probe nuclei, and carried out at room temperature and liquid nitrogen temperature, in order to investigate dynamic and static hyperfine interactions, respectively. The biomolecule samples were directly marked with the radioactive parent nuclei, whose atom link to a certain site in the biomolecules. The biological materials as well as the probe nuclei were chosen to investigate the possibility to use PAC spectroscopy to measure hyperfine parameters at nuclei from metallic elements bound to biomolecules (including the use of different probe nuclei produced in the decay of parent nuclei of four different metals) and also to study the behavior of different biomolecules by means of the measured hyperfine parameters. Results show differences in the hyperfine interactions of probe nuclei bound to the studied biomolecules. Such differences were observed by variations in the hyperfine parameters, which depend on the type of biomolecule and the results also show that the probe nuclei atom bound to the molecule in some cases and in others do not.

A great deal of theoretical activity has resulted from blending the fields of computer science and quantum mechanics. Out of this work has come the concept of a quantum computer, which promises to solve problems currently intractable for classical computers. This promise has, in turn, generated a large amount of effort directed toward investigating quantum computing experimentally. ¶ Quantum computing is difficult because fragile quantum superposition states of the computer’s register must be protected from the environment. This is made more difficult by the need to manipulate and measure these states. ¶ This thesis describes work that was carried out both to investigate and to demonstrate the utility of rare earth ion dopants for quantum computation. Dopants in solids are seen by many as a potential means of achieving scalable quantum computing. Rare earth ion dopants are an obvious choice for investigating such quantum computation. Long coherence times for both optical and nuclear spin transitions have been observed as well as optical manipulation of the spin states. The advantage that the scheme developed here has over nearly all of its competitors is that no complex nanofabrication is required. The advantages of avoiding nano-fabrication are two fold. Firstly, coherence times are likely to be adversely effected by the “damage” to the crystal structure that this manufacture represents. Secondly, the nano-fabrication presents a very serious difficulty in itself. ¶ Because of these advantages it was possible to perform two-qubit operations between independent qubits. This is the first time that such operations have been performed and presents a milestone in quantum computation using dopants in solids. It is only the second time two-qubit operations have been demonstrated in a solid. ¶ The experiments performed in this thesis were in two main areas: The first was the characterisation of hyperfine interactions in rare earth ion dopants; the second, simple demonstrations directly related to quantum computation. ¶ The first experiments that were carried out were to characterise the hyperfine interactions in Pr[superscript 3]+:Y[subscript 2]SiO[subscript 5]. The characterisation was the first carried out for the dopants in a site of such low symmetry. The resulting information about oscillator strengths and transition frequencies should prove indispensable when using such a system for quantum computation. It has already enabled an increase in the coherence times of nuclear spin transitions by two orders of magnitudes. ¶ The experiments directly related to the demonstration of quantum computation were all carried out using ensembles. The presence of a significant distribution of resonant frequencies, or inhomogeneous broadening, meant that many different sub-ensembles could be addressed, based on their resonant frequencies. Furthermore, the properties of the sub-ensembles could be engineered by optically pumping unwanted members to different hyperfine states away from resonance with the laser. ¶ A previously demonstrated technique for realising ensembles that could be used as single qubits was investigated and improved. Also, experiments were carried out to demonstrate the resulting ensembles’ utility as qubits. Further to this, ions from one of the ensembles were selected out, based on their interaction with the ions of another. Elementary two qubit operations were then demonstrated using these ensembles.

Made available in DSpace on 2014-10-09T12:33:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:00Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

In the present work we performed electronic structure calculations within the Kohn-Sham scheme of the density functional theory (DFT). We studied two molecules with potential applications in life sciences and medicine: ferrioxamine B and 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H (TMPyP) porphyrin. We used different methods and different exchange and correlation functionals, analyzing optical and vibrational properties and hyperfine interactions. In the case of ferrioxamine B, results in the crystalline phase (molecular crystal), and gas phase were compared with experimental results obtained using Mössbauer spectroscopy from the literature. We analyzed hyperfine parameters such as the electric quadrupole splitting, asymmetry parameter, hyperfine field and isomer shift. In the case of TMPyP porphyrin we analyzed vibrational properties in the gas phase and optical properties. For the electronic absorption, solvent effects and electronic charges states were analyzed. / In the present work we performed electronic structure calculations within the Kohn-Sham scheme of the density functional theory (DFT). We studied two molecules with potential applications in life sciences and medicine: ferrioxamine B and 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H (TMPyP) porphyrin. We used different methods and different exchange and correlation functionals, analyzing optical and vibrational properties and hyperfine interactions. In the case of ferrioxamine B, results in the crystalline phase (molecular crystal), and gas phase were compared with experimental results obtained using Mössbauer spectroscopy from the literature. We analyzed hyperfine parameters such as the electric quadrupole splitting, asymmetry parameter, hyperfine field and isomer shift. In the case of TMPyP porphyrin we analyzed vibrational properties in the gas phase and optical properties. For the electronic absorption, solvent effects and electronic charges states were analyzed.

Made available in DSpace on 2014-10-09T12:33:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:00Z (GMT). No. of bitstreams: 0 / O presente trabalho realiza a investigação dos parâmetros hiperfinos, incluindo a sua natureza dinâmica, em compostos ligantes em solução a temperatura ambiente (295 K) e resfriada (77K) através da espectroscopia de Correlação Angular γγ Perturbada (CAP). Para a realização das medidas experimentais, utilizou-se núcleos de prova radioativos de 111In111Cd, 181Hf181Ta e 111mCd111Cd, que decaem através de cascata gama. As amostras foram preparadas diluindo-se soluções com os núcleos radioativos em água, quando se investigou a interação do núcleo de prova com o ligante água; adicionando-se soluções com os núcleos radioativos em solução tampão, quando se investigou a interação do núcleo de prova com os íons ligantes provenientes do próprio tampão (CO32- e HCO31-) e com o OH1-; e adicionando-se soluções com os núcleos radioativos em soluções do ligante ácido etilenodiaminotetracético (EDTA), este em pH entre 4,0 e 5,0, (que corresponde ao pH da própria solução saturada do EDTA) e em solução tampão de pH entre 9 e 10. Assim foi possível investigar os efeitos gerados por cada um desses métodos de preparação de amostras nas medidas CAP. Finalmente foi feita uma análise comparativa para os vários métodos de inserção dos núcleos de prova na amostra, considerando-se aspectos químicos e nucleares. A inexistência de medidas para esse tipo de amostra, justifica a importância dos resultados obtidos. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Amostras de dióxido de cério dopadas com La e Fe foram confeccionadas e caracterizadas por uma técnica nuclear baseada em interações hiperfinas conhecida como Correlação Angular Gama-Gama Perturbada (CAP). Como o composto em questão não é radioativo, foram utilizados núcleos radioativos como ponta de prova 111In 111Cd, que decaem através de uma cascata gama-gama 171-245 keV, com nível intermediário possui uma meia-vida de 84ns, spin 5/2- e um momento de quadrupolo elétrico Q= 0,83. Inicialmente uma metodologia para a produção das amostras precisou ser elaborada. As amostras de dióxido de cério e seus dopantes foram produzidas através do processo Sol-Gel, passando por uma calcinação e sinterização até a finalização da amostra. Sendo caracterizada por diversos tipos de técnicas (Difração de Raios-X e Microscopia Eletrônica de Varredura) culminando no estudo através da técnica CAP, para uma compreensão das interações quadrupolares elétricas das amostras e também a possibilidade da existência de comportamento magnético (assunto intensamente investigado dado o interesse na área da spintrônica). Os resultados encontrados foram analisados frente aos conhecimentos encontrados na literatura e as discussões foram feitas em função da variação do elemento dopante, tipos de tratamentos térmicos usados na sinterização e as diferentes temperaturas de medidas. Permitindo uma discussão e interpretação física dos resultados encontrados. / Samples of cerium dioxide doped with La and Fe were fabricated and characterized by a technique based on nuclear hyperfine interactions known as Perturbed Angular Gamma-Gamma Correlation (PAC). As the used compound is not radioactive and the PAC technique requires a radioactive decaying through a cascade gamma-gamma, a radioactive probe nuclei were used (111In 111Cd - 171-245 keV), with intermediate has a half-life of 84ns, spin 5/2- and a moment of electric quadrupole Q= 0,83. Initially a methodology for the production of the samples had to be prepared. The cerium dioxide and its dopants were produced by the Sol-Gel process, undergoing a calcining and sintering. The sample are characterized by various types of techniques (X-ray Diffraction and Scanning Electron Microscopy) succeeding study through hyperfine Interactions, with the PAC technique, to an understanding of the electric quadrupole inteirações samples and also the possibility of the existence of magnetic behavior (subject intensively investigated given the interest in the field of spintronics). The results were analyzed taking the knowledge found in the literature and discussions were made on the basis of the variation of the doping element, thermal treatments used in the sintering temperatures and the different measures. Allowing a discussion and physical interpretation of results.

Magnetic nanoparticles offer a plethora of application possibilities in various fields of human endeavors. The fundamental understanding of their physical properties, related to the constituent magnetic phase, surface termination, and possible coating, synthesis method, size, shape, or even clustering, is crucial for their effective use and optimization for the intended applications. This thesis aims to contextualize original results, concerning especially the structure and magnetic properties, obtained during fundamental research on nanoparticles of selected iron-containing systems and employ these findings in testing the nanoparticles in chosen applications. Iron presents an ideal constituting element due to its low cost, high abundance in the Earth's crust, exploitability, and low toxicity. The selected systems involved in this thesis comprise iron-containing oxides (ferrites, and various polymorphs of iron(III) oxide, including ε-Fe2O3 and doped counterparts), and sulfides (greigite, chalcopyrite), all of which exhibit specific properties such as magnetic or structural transitions. Among the studied applications, the largest attention is devoted to the use of magnetic nanoparticles as contrast agents in magnetic resonance imaging, and the analysis of their efficacy in contrast enhancement -...