Made available in DSpace on 2014-06-11T19:35:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-11Bitstream added on 2014-06-13T19:46:44Z : No. of bitstreams: 1 santos_cm_dr_bauru.pdf: 6826027 bytes, checksum: 1ad686f4be17bb277f0631a83afd94f0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Nesse trabalho foi realizado o processo de síntese, e a caracterização estrutural e magnética de compostos HoMn1-x(Ni, Co)xO3 de estrutura perovskita. As sínteses das amostras foram realizadas por meio do método dos precursores poliméricos modificado. Após a síntese e a remoção do solvente, a resina polimérica formada foi tratada em 350ºC/4h para a remoção dos constituintes orgânicos, seguida de tratamentos térmicos em 500ºC/4h e 900ºC/20h para obtenção da fase cristalina. Para a caracterização estrutural foi utilizada a linha D10B-XPD do Laboratório Naiconal de Luz Síncrotron (LNLS), onde comprimentos de onda de raios X abaixo da borda de absorção do cobalto, do maganês e do níquel, foram utilizados. A formação das fases HoNi0.50Mn0.50O3, HoCo0.50O3 e HoNi0.25Co0.25Mn0.50O3, foram observadas pelas técnica da difração de raios X. Com o método de refinamento Reitveld para a amostra HoNi0.25Co0.25Mn0.50O3, foi determinado que o cobalto e o níquel apresentaram ocupações similares, no topo e na base da cela unitária, enquanto que o manganês ocupou preferencialmente o plano 002. A resposta magnética das amostras foi estudada através de curvas de magnetização em função da temperatura, e do campo magnético aplicado. As curvas ZFC demonstraram uma resposta paramagnética associada ao momento magnético do hólmio, além da coexistência de ferromagnetismo, antiferromagnetismos e ferrimagnetismo, devido às sub-redes formadas pelos metais de transição. As curvas FC evidenciaram o fenômeno da inversão de spin, associado à interação entre as sub-redes formadas pelos metais de transição com a sub-rede formada pela terra-rara, considerando um mecanismo de interação de troca antiferromagnética / In this work was accomplished the syntheis process and structural and magnetic characterization of HoMn1-x(NiCo)xO3 compounds of pervskites structure. The sample synthesis were performed through modified polymeric precursos method. After synthesis and solvent removal, the polymer resin formed was treated at 350ºC/4h for organic constituents removal, followed by heating treatment at 500ºC/4h and 900ºC/20h to obtain the crystalline phase. For structural characterization, it was used D10B-XPD beam line of Laboratório Nacional de Luz Síncrotron (LNLS), where X-rays wavelengths below cobalt, manganeses and nickel absorption edge, were used. The formation of HoNi0.50Mn0.50O3, HoCo0.50O3 e HoNi0.25Co0.25Mn0.50O3 phases were observed by X-ray diffraction technique. By Rietveld refinement method for sample HoNi0.25Co0.25Mn0.50O3, it was determined that cobalt and nickel had similar occupations at the top and bottom of unit cell, while the manganeses preferentially occupied plan 002. The magnetic response of samples was studied through magnetization curves according to the temperature function and the applied magnetic field. The ZFC curves showed a paramagnetic response associated to holmium magnetic moment, and ferromagnetism, antiferromagnetism and ferrimagnetism coexistence, due to sublattices formed by transition metals. The FC curves evidenced the spin reversal phenomenon, associated to the interaction between the sublattice formed bu transition metals with sublattices formed by rare-earth, considering a mechanism of antiferromagnetic exchange interaction

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto. / Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007. / Includes bibliographical references. / The origin of symmetric alternating magnetic polarity stripes on the seafloor is investigated in two marine environments; along the ridge axis of the fast spreading East Pacific Rise (EPR) (90 25'-90 55'N) and at Kane Megamullion (KMM) (230 40'N), near the intersection of the slow-spreading Mid Atlantic Ridge with Kane Transform Fault. Marine magnetic anomalies and magnetic properties of seafloor samples are combined to characterize the magnetic source layer in both locations. The EPR study suggests that along-axis variations in the observed axial magnetic anomaly result from changing source layer thickness alone, consistent with observed changes in seismic Layer 2a. The extrusive basalts of the upper crust therefore constitute the magnetic source layer along the ridge axis and long term crustal accretion patterns are reflected in the appearance of the axial anomaly. At KMM the C2r.2r/C2An. In (- 2.581 Ma) polarity reversal boundary cuts through lower crust (gabbro) and upper mantle (serpentinized peridotites) rocks exposed by a detachment fault on the seafloor, indicating that these lithologies can systematically record a magnetic signal. Both lithologies have stable remanent magnetization, capable of contributing to the magnetic source layer. The geometry of the polarity boundary changes from the northern to the central regions of KMM and is believed to be related to changing lithology. In the northern region, interpreted to be a gabbro pluton, the boundary dips away from the ridge axis and is consistent with a rotated conductively cooled isotherm. In the central region the gabbros have been removed and the polarity boundary, which resides in serpentinized peridotite, dips towards the ridge axis and is thought to represent an alteration front. The linear appearance of the polarity boundary across both regions indicates that the two lithologies acquired their magnetic remanence during approximately the same time interval. Seismic events caused by detachment faulting at Kane and Atlantis Transform Faults are investigated using hydroacoustic waves (T-phases) recorded by a hydrophone array. Observations and ray trace models of event propagation show bathymetric blockage along propagation paths, but suggest current models of T-phase excitation and propagation need to be improved to explain observed characteristics of T-phase data. / by Clare Margaret Williams. / Ph.D.

Orientador: Paulo Noronha Lisboa-Filho / Banca: Fabio Furlan Ferreira / Banca: Manuel Henrique Lente / Banca: André Maurício Brinatti / Banca: Guinther Kellermann / O Programa de Pós graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP / Resumo: Nesse trabalho foi realizado o processo de síntese, e a caracterização estrutural e magnética de compostos HoMn1-x(Ni, Co)xO3 de estrutura perovskita. As sínteses das amostras foram realizadas por meio do método dos precursores poliméricos modificado. Após a síntese e a remoção do solvente, a resina polimérica formada foi tratada em 350ºC/4h para a remoção dos constituintes orgânicos, seguida de tratamentos térmicos em 500ºC/4h e 900ºC/20h para obtenção da fase cristalina. Para a caracterização estrutural foi utilizada a linha D10B-XPD do Laboratório Naiconal de Luz Síncrotron (LNLS), onde comprimentos de onda de raios X abaixo da borda de absorção do cobalto, do maganês e do níquel, foram utilizados. A formação das fases HoNi0.50Mn0.50O3, HoCo0.50O3 e HoNi0.25Co0.25Mn0.50O3, foram observadas pelas técnica da difração de raios X. Com o método de refinamento Reitveld para a amostra HoNi0.25Co0.25Mn0.50O3, foi determinado que o cobalto e o níquel apresentaram ocupações similares, no topo e na base da cela unitária, enquanto que o manganês ocupou preferencialmente o plano 002. A resposta magnética das amostras foi estudada através de curvas de magnetização em função da temperatura, e do campo magnético aplicado. As curvas ZFC demonstraram uma resposta paramagnética associada ao momento magnético do hólmio, além da coexistência de ferromagnetismo, antiferromagnetismos e ferrimagnetismo, devido às sub-redes formadas pelos metais de transição. As curvas FC evidenciaram o fenômeno da inversão de spin, associado à interação entre as sub-redes formadas pelos metais de transição com a sub-rede formada pela terra-rara, considerando um mecanismo de interação de troca antiferromagnética / Abstract: In this work was accomplished the syntheis process and structural and magnetic characterization of HoMn1-x(NiCo)xO3 compounds of pervskites structure. The sample synthesis were performed through modified polymeric precursos method. After synthesis and solvent removal, the polymer resin formed was treated at 350ºC/4h for organic constituents removal, followed by heating treatment at 500ºC/4h and 900ºC/20h to obtain the crystalline phase. For structural characterization, it was used D10B-XPD beam line of Laboratório Nacional de Luz Síncrotron (LNLS), where X-rays wavelengths below cobalt, manganeses and nickel absorption edge, were used. The formation of HoNi0.50Mn0.50O3, HoCo0.50O3 e HoNi0.25Co0.25Mn0.50O3 phases were observed by X-ray diffraction technique. By Rietveld refinement method for sample HoNi0.25Co0.25Mn0.50O3, it was determined that cobalt and nickel had similar occupations at the top and bottom of unit cell, while the manganeses preferentially occupied plan 002. The magnetic response of samples was studied through magnetization curves according to the temperature function and the applied magnetic field. The ZFC curves showed a paramagnetic response associated to holmium magnetic moment, and ferromagnetism, antiferromagnetism and ferrimagnetism coexistence, due to sublattices formed by transition metals. The FC curves evidenced the spin reversal phenomenon, associated to the interaction between the sublattice formed bu transition metals with sublattices formed by rare-earth, considering a mechanism of antiferromagnetic exchange interaction / Doutor

The scope of this thesis is the study of the interplay between structure and magnetism in amorphous materials. The investigations focus on the growth of amorphous layers and the study of the influence of structural disorder and reduced physical extension on the magnetic properties of thin films and multilayers. The examined magnetic materials are FeZr alloys, as well as other amorphous transition metal alloys such as CoZr and FeCoZr. Thin films and multilayers of the studied materials were deposited using magnetron sputtering in ultra-high vacuum conditions. Their amorphous structure and layering quality was investigated using X-ray scattering techniques and in several cases with transmission electron microscopy. The chemical composition of the alloys was determined with Rutherford Backscattering Spectrometry. The magnetic properties were investigated using the magneto-optic Kerr effect and SQUID magnetometry, as well as polarized neutron reflectometry and X-ray magnetic circular dicroism measurements. For FeZr alloys deposited as multilayers with Al2O3 as spacer layer, it was found that Fe-rich nanocrystallites, formed at the metal/oxide interfaces, exert large influence on the magnetic properties. The use of AlZr alloys as buffer layers promotes the growth of highly amorphous FeZr layers. FeZr/AlZr multilayers with good layering quality can also be obtained. The influence of the reduced layer thickness on the magnetic moment, Curie temperature and magnetic dimensionality of the magnetic layers is addressed for FeZr/AlZr multilayers. Thin FeZr layers in these structures are found to belong to the 2D XY dimensionality class. The change of the magnetic moment and Curie temperature with reduced FeZr layer thickness is quantified. In addition, the induced magnetic moment in the alloy element Zr was investigated in FeZr and CoZr alloy films. The possibility to imprint a preferred magnetization direction during thin film preparation was demonstrated for FeCoZr layers. Lastly, AlZr alloy films were studied with respect to their oxidation stability at room and elevated temperatures, aiming towards development of materials with passivating properties.

In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed. In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model. One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements. Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization. / QC20100708

In the course of these investigations altogether 18 different compounds have been synthesized and their chemical, structural and physical properties were characterized (XRD, XANES, IR, Raman spectrum, magnetic susceptibility, electrical resistivity, low temperature and TG/DTA). Up to now only nitridonickelates and nitridocuprates were known to exhibit exclusively low oxidation states of the transition metals between 0 and +2. In this work it has been presented that also nitridocobaltates belong to this group. We have proved that “Ca3CoIIIN3” do not exist and the real chemical formula can be regarded as Ca5[CoIN2]2. In the thesis another seven new nitridocobaltates(I) have been described, these add to four already known structures. Among novel phases only Ba9Ca[Co2N3]3 may indicate higher valency state for cobalt with the [Co2N3]5- complexes. The XANES data supporting CoII state by comparison with other compounds possess this oxidation state. The crystal structure of Ba9Ca[Co2N3]3 is related to the perovskite type structure. The remarkable structural features of Sr2[CoN2]0.72[CN2]0.28 ≈ Sr6[CoN2]2[CN2] nitridocobaltates [CoIN2]5- ions partially substituted by carbodiimides [N=C=N]2- ions. Up to now in the crystal structure no indications for a homogeneity range could be observed. Both crystal structures of (Sr6N)[CoN2][CN2]2 and Sr6[CoN2]2[CN2] encompass nitridocobaltate [CoN2]5- and carbodiimide [N=C=N]2- ions. In the structures distorted rocksalt motif based on Sr-N partial structure can be distinguished. Up to now in the system AE-Fe-N-(C) only four crystal structures were reported and in the thesis three new were refined Sr8[FeIIIN3]2[FeIIN2], Sr3[FeN3] and (Sr6N)[FeN2][CN2]2 and their physical properties were characterized. The system AE-Mn-N-(C) via this work was extended by Sr8[MnN3]3 and Sr4[MnN3][CN2]. Up to date the only nitridometalate containing different transition elements is Ba[Ni1-xCuxN]. In this work one more mixed nitridometalate has been described Sr8[MnIIIN3]2[FeIIN2]. The crystal structure of Sr4[MnN3][CN2] revealed some weak diffuse scattering lines. The general formula of Sr4[MnN3][CN2] can be written as Sr4[Mn0.96N2.90][C0.96N2] to emphasize possible homogeneity range. Any explanation of the phenomena and establishment of possible homogeneity range are still a challenge. The structures of Sr8[MIIIN3]2[FeIIN2] (M = Mn, Fe) are related to Sr8[MnIVN3]2[MnIIIN3]. All these compounds are first mixed-valency compounds for respective systems and exhibit close relation to crystal structures of Sr3[MN3] (M = Mn, Fe). From the XANES data alike behaviour of all structures containing Mn was observed. Due to some possible degree of Mn/Fe mixing in the crystal structure of Sr8[MIIIN3]2[FeIIN2] the chemical formula might be written as Sr8[MnN3]2-x[FeN3]x[FeN2]. This needs to be investigate in details. Up to now in the literature the only crystallographic data of nitridometalates contain [NCN]2- ions include two compounds. In this work four novel nitridometalate carbodiimides and cyanamides Sr4[MnN3][CN2], (Sr6N)[MN2][CN2]2 (M = Co, Fe) and Sr6[CoN2]2[CN2] have been synthesized. Predominant magnetic properties in the investigated nitridometalates are connected to some antiferromagnetic M-M interactions supported by AFM ordering. The electrical resistivity often shows at some semi-conducting character of these compounds. XANES spectroscopy provided many useful data about valency states of the transition elements, coordination environment around absorbing atoms and electronic structure. The influence of different parameters on the transition metals K-edges was studied in details. IR and Raman give general data about [NCN]2- ions.

<p>In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested.</p><p>In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model.</p><p>One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement.</p>

A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras e Cerâmicos à temperatura ambiente de baixo custo e de implementação mais simples. Para isso, o Histerisímetro de Entreferro Variável, HEV, é concebido e estudado. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável, bobinas de magnetização e desmagnetização de baixa potência, uma sonda de efeito Hall com seu respectivo gaussímetro, um fluxímetro com sua bobina exploradora, o circuito eletrônico de comando das bobinas de excitação e a interface a um sistema de instrumentação virtual. Para demonstrar os desenvolvimentos do trabalho são apresentados o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo em relação aos ímãs permanentes, instrumentação necessária para sua caracterização, a concepção e modelagem do HEV, os resultados dos testes realizados e uma abrangente análise de suas incertezas. Com isso é demonstrado que o Histerisímetro de Entreferro Variável é uma alternativa de caracterização de ímãs permanentes com desmagnetização linear com incertezas dentro do que é definido pela norma. / The determination of the main magnetic properties of permanent magnets usually requires sophisticated and expensive measuring systems. This work analyses and proposes a low-cost system for the characterization of Rare Earth and Ceramics permanent magnets at room temperature with simpler implementation. It comprehends a magnetic circuit with the permanent magnet under test, a steel yoke with appropriate pole pieces, a variable air gap, low power magnetization and demagnetization coils, a Hall Effect probe with its respective gaussmeter, a fluxmeter with its own search coil, a coil driver electronic circuit and a virtual instrumentation system (computer plus graphical interface software). To demonstrate the developments of the work, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism related to permanent magnets, the instrumentation required for its characterization, the HEV design and modeling, the results of the tests and a comprehensive analysis of related uncertainties. Thus, it is shown that the Variable Gap Hysteresimeter is an alternative characterization system for linear demagnetization permanent magnets with uncertainties within those defined by the standards.