Nanomateriais de fct-FePt, SmCo e Carbeto de Cobalto têm sido bastante estudados para a aplicação em gravação magnética e imãs de elevado desempenho, devido as suas energias magnetocristalinas e coercividades elevadas. Nanopartículas de FePt unidimensionais foram propostas na tentativa de obter melhora no alinhamento magnético das estruturas auto-organizadas. Neste trabalho, a formação de nanobastão e nanofios de FePt foi estudada através da presença de oleilamina e pequena quantidade de monóxido de carbono liberado pelo pentacarbonilferro(0). Estes dois parâmetros foram estudados a fim de analisar a influência no alongamento das nanopartículas e verificou-se que ambos atuam sinergicamente. Foram obtidos tanto nanofios de FePt ramificados de comprimento de 20-100 nm quanto nanobastões de FePt de 20-60 nm de comprimento, ambos com diâmetro de 2-3 nm. Todas as nanopartículas sintetizadas foram obtidas na fase cúbica de face centrada e o processo de tratamento térmico nas temperaturas de 450 oC e 560 oC levou a conversão para a fase tetragonal de face centrada, com custo da sinterização das nanopartículas. Os nanobastões, entretanto, apresentaram maior estabilidade térmica se comparado com o nanofio ramificado, obtendo propriedade ferromagnética na amostra. Alternativamente, têm sido obtidos satisfatoriamente nanobastões de platina para posterior recobrimento com ferro para a formação da liga FePt após o processo de recozimento. Na síntese de SmCo, foi estudada a formação da liga diretamente por via química através do uso de redutores comumente utilizandos em síntese de nanopartículas, porém foi possível observar apenas uma pequena quantidade da liga Sm2Co17 quando se utiliza o boroidreto de sódio. Isto se deve, principalmente, ao alto potencial de redução de Sm3+ e a sua instabilidade química. Entretanto, foram desenvolvidos métodos promissores para a obtenção de nanopartículas de CoO e SmCoO com tamanho e forma controlada. Além destes sistemas, tem sido obtidas diretamente através de síntese química nanopartículas de carbeto de cobalto com coercividade de até 2,3 kOe e magnetização de 45 emu/g, além de desenvolver um método geral de síntese de carbetos de outros metais. / SmCo, fct-FePt and CoC nanomaterials have been studied for application in magnetic recording and permanent magnets due to theirs high coercivity and magnetocrystalline anisotropy. One-dimensional FePt nanoparticles were proposed to improve the magnetic alignment of self-assembled system. In this work, the formation of FePt nanorods and nanowires was studied by using a small amount of carbon monoxide from the precursor pentacarbonyliron(0) and oleylamine. Both parameters of synthesis were studied and was verified that they influence the one-dimensional growth of FePt. In fact, branched FePt nanowires with 20 - 100 nm of length and nanorods with 20 - 60 nm were obtained, both with 2-3 nm of diameters. The FePt nanoparticles were obtained in face centered cubic phase and the transformation to face centered tetragonal phase was carry out in the temperatures of 450 oC and 560 oC, which led the formation of sintered nanoparticles. FePt nanorods have better thermal stability than nanowires according the results obtained. The platinum nanorods covered with iron oxide also were obtained to formation of FePt by thermal treatment. In concern of SmCo syntheses, the formation of SmCo phase directly by chemical synthesis was investigated by using some reduction agent, but was obtained a small amount of smco phase only if the sodium borohydrate was used in the synthesis. This could be occurred due to high reducing potential of Sm3+ and its chemical instability. However, some methods were obtained to obtain CoO and SmCoO nanoparticles with size and shape control. Furthermore, cobalt carbide nanoparticles were well obtained with coercivity of 2,3 kOe and magnetization of 45 emu/g, and a new general method to obtain metals carbides was developed.

O objetivo do presente trabalho foi desenvolver novos materiais magnéticos para ímãs de alta performance. Duas classes de materiais foram estudadas: materiais a base de (Nd,Sm)5(Fe,MT)17, onde MT é um metal de transição, e materiais nanocristalinos a base de (Nd,Pr)FeB com adições de TiC. As ligas (Nd,Sm)5(Fe,MT)17 foram preparadas por fusão em forno de arco e posteriormente foram tratadas termicamente por longos períodos (no mínimo 30 dias). Tentamos melhorar as propriedades magnéticas por meio de substituições químicas (Ti, Co, Mn, etc.) e/ou por introdução intersticial de deutério ou nitrogênio. As amostras foram caracterizadas via análise termomagnética (TMA), magnetometria de baixas temperaturas, difração de raios X e de nêutrons, e espectroscopia Mössbauer. Os principais resultados foram: a) aumento de Tc de até 70 º C; b) localização dos átomos de deutério na redecristalina. Ligas de (Nd,Pr) com adição de TiC foram preparadas por fusão de arco, sendo processadas via "melt spinning" e passando por tratamentos térmicos variados. Os promissores resultados na literatura para Nd2Fe14B+TiC foram obtidos também para Pr2Fe14B + TiC, mas não para os sistemas compostos pela fase φ e Fe3B com TiC. Porém, bons resultados foram obtidos em sistemas compostos pelas fases φ e α–Fe, com aumento de até 30% nos valores de campo coercivo Hc e aumentos de até 15% de (BH)max. / The aim of the present work was to develop new improved magnetic materials suitable for permanent magnets. Two kinds of materials were studied: (Nd,Sm)5(Fe,MT)17 based materials, were MT is a transition metal and, (Nd,Pr)FeB nanocrystalline materials (exchange spring magnets) with TiC additions. The 5:17 alloys were melted in an arc melting furnace followed by a long annealing (at least 30 days). We tried to improve the magnetic properties by means of chemical substitutions (Ti, Co, Mn, etc.) and/or by addition of interstitial atoms of deuterium or nitrogen. The samples were characterized by means of thermomagnetic analysis (TMA), low temperature magnetometry, X ray and neutron diffraction, and Mössbauer spectroscopy. The main results were: a) increase of Tc temperature (up to 70 ºC) and; b) determination of interstitial sites for deuterium. (Nd,Pr)FeB alloys with TiC additions were melted in an arc melting furnace, being processed in a melt spinner system. After the samples were heat treated at different temperatures. The promissing literature results for Nd2Fe14B+TiC were also obtained for Pr2Fe14B + TiC, but not for systems composed by Pr2Fe14B and Fe3B phases with TiC additions. However, good results were obtained in systems composed by Pr2Fe14B and α-Fe with TiC additions, with 30% increase on coercive field values Hc, and 15% increase on (BH)max.

Thermomagnetic motors can represent an alternative for the conversion of heat into mechanical energy, limited by the critical transition temperature (TC) of the used magnetic materials. Thus, by using materials with a TC close to room temperature, the energy available in the form of low-grade heat sources can be converted into useful mechanical work. This thesis proposes the development of a thermomagnetic motor to be operated with heat sources at temperatures in the range from 343 to 353 K, and a heat sink at room temperature, using water as the heat transfer fluid, presenting a novel approach to the construction of thermomagnetic devices. The design of this thermomagnetic motor was developed with the intent of producing a rotary movement, working similarly to an electric stepper motor, where instead of the electromagnetic coils being activated by an electric current, plates of a magnetic material change their magnetization state, due to a change in their temperature caused by the heat transfer with the heat transfer fluid. The analysis of the thermomagnetic motor proposed was done with the adoption of an integrated approach of numerical simulation and experimental validation. The evaluation of the motor is divided into the three main physical phenomena it encompasses: the magnetic field source, the heat transfer processes involved in the change of temperature of the magnetic material, and the system dynamics and power production. Each of these systems was modeled using computational tools. These models were then validated according to the data measured, obtained from a test stand of an idealized thermomagnetic motor, and for a rotary thermomagnetic motor. This methodology allowed a more comprehensive understanding of the critical working principles of the motor developed, and with that a fast advancement of the technology through a validated computational model. The computational models helped to identify the critical components to be improved in the development of these motors. These parameters can be guidelines for the design of thermomagnetic motors. One of the ways identified to produce a significant performance improvement, in the simulations, was the adoption of a control strategy that promotes the regeneration of heat in the plates of magnetic material, through which an improvement in the efficiency of 2.7 times could be achieved. / Motores termomagnéticos representam uma alternativa para a conversão de calor em energia mecânica, limitada apenas pela temperatura crítica da transição termomagnética (TC) dos materiais magnéticos. Ao usar materiais com TC próximo à temperatura ambiente, pode-se realizar a conversão da energia contida nas chamadas fontes pobres de calor, produzindo trabalho mecânico útil. Esta tese propõe o desenvolvimento de um motor termomagnético para operação com fontes de calor com temperaturas entre 343 e 353 K, e resfriamento à temperatura ambiente, utilizando a água como fluído de troca térmica, apresentando uma abordagem inovadora para dispositivos termomagnéticos. O motor foi projetado para produção de movimento rotativo de um eixo, per meio de um princípio similar ao de um motor de passo, no qual em vez de bobinas ativadas pela passagem de corrente elétrica, placas de material magnético sofrem uma mudança em seu estado de magnetização, devido à mudança de temperatura, causada pela troca de calor com a água. A análise do motor termomagnético proposto foi realizada com a adoção de uma abordagem integrada de simulações numéricas e validação experimental, dividindo a avaliação dos motores nos três principais fenômenos físicos envolvidos em seu funcionamento: a fonte de campo magnético, o processo de troca térmica envolvido na mudança de temperatura do material magnético, a dinâmica do sistema e produção de potência. Cada um destes sistemas foi modelado usando ferramentas computacionais. Os resultados obtidos foram então validados utilizando dados experimentais, obtidos a partir da construção e caracterização de uma bancada de testes para um motor termomagnético idealizado, e também para o motor termomagnético rotativo construído. Esta metodologia propiciou maior entendimento das funções críticas do motor desenvolvido, e possibilitou ainda sua otimização, através do estudo dos modelos computacionais validados. Os parâmetros obtidos ajudaram a identificar componentes críticos para melhoria no projeto do motor rotativo construído, e servem também como guias gerais para projetos de motores termomagnéticos. Um dos componentes com elevado potencial de melhoria foi a adoção de uma estratégia de controle para a regeneração do calor nas placas de material magnético, o que possibilitou, nas simulações, uma melhoria até 2,7 vezes na eficiência.

Dispositivos spintrônicos baseados no transporte de corrente polarizada em spin, torque de spins e em outros fenômenos representam grandes promessas no cenário da tecnologia de miniaturização dos dispositivos eletrônicos da atualidade. Materiais magnéticos de grande relevância tecnológica para diferentes áreas envolvem, apesar de exceções, filmes e estruturas multicamadas com alta complexidade. Avanços nesta área exigem o da estrutura das mesmas, em escala atômica, possibilitando o ajuste de suas propriedades físicas. O propósito deste trabalho é a preparação de estruturas multicamadas por sputtering, bem como o estudo de fenômenos magnéticos envolvidos nestas estruturas. O objetivo é produzir uma válvula de spin. Esta é uma estrutura multicamada composta por dois filmes ferromagnéticos separados por um espaçador não magnético. A magnetização de uma das camadas ferromagnéticas é livre para girar sob efeito de pequenos campos externos, enquanto a magnetização da outra camada ferromagnética permanece fixada por meio de acoplamento de troca com uma camada antiferromagnética. A estrutura é ajustada para permitir que pequenos campos magnéticos aplicados possam chavear a magnetização das camadas ferromagnéticas, de um estado antiparalelo à um estado paralelo, resultando na variação da resistividade elétrica da estrutura (efeito GMR). Otimização das condições de deposição foi necessária para obter estruturas com acoplamento por polarização de troca, e acoplamento antiferromagnético através do espaçador não magnético. A correlação entre as condições de deposição e as propriedades magnéticas dos filmes foi estudada. O trabalho apresentado nesta dissertação tem contribuído para a caracterização de filmes finos magnéticos, quais podem ser utilizados na produção de sensores magnéticos, e do novo sistema de sputtering montado no Laboratório de Física Aplicada do CDTN. / Spintronic devices based in the transport of spin polarized current, spins torque and other related phenomena represent big promises in the scenery of the technological miniaturization of current electronic devices. Magnetic materials of great technological relevance for different areas deal with, despite some exceptions, films and multilayered structures with high complexity. Advances on these fields require the control of those structures in atomic scale, in order to be able to tailor their physical properties. The purpose of this work is the preparation of multilayered structures by sputtering, as well the study of magnetic phenomena involved in this structures. The aim is to produce a spin valve. This is a multilayer structure composed of two ferromagnetic layers, separated by a non magnetic spacer. The magnetisation of one of the ferromagnetic layers is free to rotate under the effect of small external fields, whilst the magnetisation of the other ferromagnetic layer remains fixed by means exchange coupling to a antiferromagnetic layer. The structure is tailored to allow the small applied magnetic fields to switch the magnetisation of the ferromagnetic layers from antiparallel state to a parallel state resulting in the variation of the electrical resistivity of the structure (GMR effect). Optimization of deposition conditions was required to obtain structures with exchange bias coupling, and antiferromagnetic coupling through a non magnetic spacer. The correlation between the deposition conditions and the magnetic properties of the films was studied. The work presented in this dissertation has contributed to the characterisation of both magnetic thin films, which can be used on the production of magnetic sensors, and the new sputtering system assembled in the Applied Physics Laboratory of CDTN.

Imãs são corpos de materiais magnetizáveis utilizados para gerar um forte campo magnético em sua vizinhança. Essa característica faz com que sejam empregados em diversas aplicações na vida moderna, tais como motores para a indústria eletroeletrônica e automobilística, como elementos de fixação e em acoplamentos magnéticos na indústria mecânica. O mercado de ímãs permanentes movimenta atualmente cerca de US$ 5 bilhões por ano e está em plena expansão, sendo estimado um crescimento de 12% por ano até o final desta década de 90. Tal crescimento é atribuído aos \"novos materiais\" desenvolvidos a partir da década de 80 (ímãs de terras-raras) e aos novos mercados, que foram gerados pelos próprios \"novos materiais\" (Hart, 1996). Tratando-se de materiais tão ligados às facilidades da vida moderna, a pesquisa na área de imãs está intimamente ligada ao seu desenvolvimento tecnológico. Procura-se desenvolver imãs com as melhores propriedades magnéticas para as suas aplicações, investigando ao mesmo tempo os fenômenos que regem os mecanismos físicos de magnetização. / Permanent magnets composed of magnetic powders bonded with a polymer represent the fastest growing sector of the magnetic materials market since they are ideal for the fabrication of small motors. This work presents a magnetic and structural characterization of TIve eommereial bonded magnets, Reversible and irreversible components of the total magnetization as well as magnetic interactions in the five commereial magnets are also studied, the magnets are composed by ferrite and MQP-Q nanoerystelline powders and mixtures of these two powders with 80%, 60% and 40% ferrite. Magnelie interactions were analyzed by Henkel plots, gM plots and switching field distributions. In bonded magnets, since the magnetic particles are separated from each other by a binder, it is expected that interactions are mainly dipolar in Nature. There is a progressive change in the data as the fraction of MQP-Q powder is increased. The sample with 100% ferrite shows strong magnetizing interactions at low fields. Date for hybrid magnets present increasing demagnetizing interactions as the fermion of MQP-Q increases and for the 100% MQP-Q sample, the data indicate demagnetizing effects. Reversible and irreversible magnetization components were obtained by applying two methods commanly used in magnetic materials characterization, the DCD -IRM method and the reversible susceptibility method. For the 100% ferrite magnet, in which the reversible component is small, the methods lead lo similar results. The results for both methods diverge as the reversible component! Increases, which in this case occurs with the increase of the MQP-Q powder fraction. The divergence is attributed to the idealized conditions of non-inleracting particles assumed by the DCD-IRM method. Magnetic interactions and lotai magnetization components were also studied in a melt-spun nanocrystalline Nd9Fe85B5 sample. This composition is similar to that of the MQP-Q powder and the magnetic behavior of both the bonded magnetic and the nanocrystalline precursor could be compared. Micromagnetic simulations allowed the evaluation of exchange, anisotropy and magnetostatic interactions on the magnetization reversal of nanocryslalline romposlle systems. The Monte Carlo method was applied lo a linear array of 300 magnetic moments distributed in three grains, two magnetically hard with a soft grain between them.

With the discovery of appreciable room temperature magnetoresistance (MR) in high Curie temperature (Tc) ferrimagnetic double perovskites such as Sr2FeMoO6, research surrounding other materials of this type has expanded. Most ferrimagnetic double perovskites of the formula A2BB'O6 have non-magnetic A-site cations, such as Sr2+, Ca2+ or Ba2+. Replacing non-magnetic cations with magnetic variants offers further possibilities to tune magnetic effects. This thesis focuses on the substitution of non-magnetic A-site cations with relatively small magnetic Mn2+ cations. This substitution is made possible through the use of high-pressure/temperature (P/T) synthesis, and the characterisation of structural and magnetic properties of new phases discovered through these syntheses. The first of these new phases to be reported herein is Mn2FeReO6, which can be described as the Mn analogue of the well-known ferrimagnetic double perovskite Ca2FeReO6. These materials are well ordered with Fe3+/Re5+ on B-sites and crystallise in a P21/n structure. Mn2FeReO6 shows a high Tc of 520 K due to ferrimagnetic Fe/Re magnetic order above RT, and a large saturated magnetisation of 5.0 μB, which peaks at 75 K. Interestingly, the A-site Mn2+ (3d5) magnetic order has the effect of causing a spin reorientation of the Fe/Re sublattice observed by neutron powder diffraction (NPD) at temperatures below ~75 K. This causes the MR to exhibit the expected negative intergrain tunnelling behaviour above the transition and colossal positive behaviour below. Also reported are a series of perovskite related structures with formulae CaxMn2- xFeReO6 (x = 0.5, 1.0, 1.5). Of particular note among these is CaMnFeReO6, which exhibits 1:1 A-site ordering of Ca/Mn and adopts the P42/n space group. This material belongs to a family of newly discovered 'double double' perovskites, in which Ca/Mn order in columns pointing along the c-axis and Mn has alternating tetrahedral and square planar coordination environments. MR in this material remains negative down to 20 K, potentially due to the presence of Ca disrupting magnetic interactions between Mn2+ cations and suppressing the spin transition. Alternating coordination environments in the double double perovskite structure type were exploited in the synthesis of Ca(Mn0.5Cu0.5)FeReO6. This material also crystallises in the P42/n structure and is well ordered on B-sites, as evidenced by X-ray powder diffraction. Neutron diffraction yields, in addition to columnar order, a slight preference for Cu to occupy the square planar sites and for Mn to occupy tetrahedral sites. This doping of square planar sites with Cu has the effect of enhancing magnetic properties compared to CaMnFeReO6, increasing the saturated magnetisation, raising the ferrimagnetic ordering temperature of the B-sites from 500 to 560 K, and also having a profound effect on the observed MR effects, as a switch in the sign of the MR is observed in this material through a magnetic transition. Finally, B-site substitution has been experimented with in the synthesis of CaMnMnReO6. This also possesses the combined A and B-site orders observed in CaMnFeReO6 and an unusual magnetic structure, with perpendicular A and B-site magnetism due to frustration, deviating greatly from the magnetic structures of materials with B-site Fe/Re. In summary, this thesis compiles the synthesis and analysis of a series of new double perovskites, double double perovskites and a new 'triple double' five-fold cation ordered structure with a general formula of AA'0.5A''0.5BB'O6. These materials show that new types of structural ordering can be used to increase the number of degrees of freedom available for tuning the interplay between many different magnetic cations in different coordination environments.

Imãs são corpos de materiais magnetizáveis utilizados para gerar um forte campo magnético em sua vizinhança. Essa característica faz com que sejam empregados em diversas aplicações na vida moderna, tais como motores para a indústria eletroeletrônica e automobilística, como elementos de fixação e em acoplamentos magnéticos na indústria mecânica. O mercado de ímãs permanentes movimenta atualmente cerca de US$ 5 bilhões por ano e está em plena expansão, sendo estimado um crescimento de 12% por ano até o final desta década de 90. Tal crescimento é atribuído aos \"novos materiais\" desenvolvidos a partir da década de 80 (ímãs de terras-raras) e aos novos mercados, que foram gerados pelos próprios \"novos materiais\" (Hart, 1996). Tratando-se de materiais tão ligados às facilidades da vida moderna, a pesquisa na área de imãs está intimamente ligada ao seu desenvolvimento tecnológico. Procura-se desenvolver imãs com as melhores propriedades magnéticas para as suas aplicações, investigando ao mesmo tempo os fenômenos que regem os mecanismos físicos de magnetização. / Permanent magnets composed of magnetic powders bonded with a polymer represent the fastest growing sector of the magnetic materials market since they are ideal for the fabrication of small motors. This work presents a magnetic and structural characterization of TIve eommereial bonded magnets, Reversible and irreversible components of the total magnetization as well as magnetic interactions in the five commereial magnets are also studied, the magnets are composed by ferrite and MQP-Q nanoerystelline powders and mixtures of these two powders with 80%, 60% and 40% ferrite. Magnelie interactions were analyzed by Henkel plots, gM plots and switching field distributions. In bonded magnets, since the magnetic particles are separated from each other by a binder, it is expected that interactions are mainly dipolar in Nature. There is a progressive change in the data as the fraction of MQP-Q powder is increased. The sample with 100% ferrite shows strong magnetizing interactions at low fields. Date for hybrid magnets present increasing demagnetizing interactions as the fermion of MQP-Q increases and for the 100% MQP-Q sample, the data indicate demagnetizing effects. Reversible and irreversible magnetization components were obtained by applying two methods commanly used in magnetic materials characterization, the DCD -IRM method and the reversible susceptibility method. For the 100% ferrite magnet, in which the reversible component is small, the methods lead lo similar results. The results for both methods diverge as the reversible component! Increases, which in this case occurs with the increase of the MQP-Q powder fraction. The divergence is attributed to the idealized conditions of non-inleracting particles assumed by the DCD-IRM method. Magnetic interactions and lotai magnetization components were also studied in a melt-spun nanocrystalline Nd9Fe85B5 sample. This composition is similar to that of the MQP-Q powder and the magnetic behavior of both the bonded magnetic and the nanocrystalline precursor could be compared. Micromagnetic simulations allowed the evaluation of exchange, anisotropy and magnetostatic interactions on the magnetization reversal of nanocryslalline romposlle systems. The Monte Carlo method was applied lo a linear array of 300 magnetic moments distributed in three grains, two magnetically hard with a soft grain between them.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

In all energy systems, the parameters necessary to calculate power are the same in functionality: an effort or force needed to create a movement in an object and a flow or rate at which the object moves. Therefore, the power equation can generalized as a function of these two parameters: effort and flow, P = effort * flow. Analyzing various power transfer media this is true for at least three regimes: electrical, mechanical and hydraulic but not for magnetic. This implies that the conventional magnetic system model (the reluctance model) requires modifications in order to be consistent with other energy system models. Even further, performing a comprehensive comparison among the systems, each system's model includes an effort quantity, a flow quantity and three passive elements used to establish the amount of energy that is stored or dissipated as heat. After evaluating each one of them, it was clear that the conventional magnetic model did not follow the same pattern: the reluctance, as analogous to the electric resistance, should be a dissipative element instead it is an energy storage element. Furthermore, the two other elements are not defined. This difference has initiated a reevaluation of the conventional magnetic model. In this dissertation the fundamentals on electromagnetism and magnetic materials that supports the modifications proposed to the magnetic model are presented. Conceptual tests to a case study system were performed in order to figure out the network configuration that better represents its real behavior. Furthermore, analytical and numerical techniques were developed in MATLAB and Simulink in order to validate our model. Finally, the feasibility of a novel concept denominated magnetic transmission line was developed. This concept was introduced as an alternative to transmit power. In this case, the media of transport was a magnetic material. The richness of the power-invariant magnetic model and its similarities with the electric model enlighten us to apply concepts and calculation techniques new to the magnetic regime but common to the electric one, such as, net power, power factor, and efficiency, in order to evaluate the power transmission capabilities of a magnetic system. The fundamental contribution of this research is that it presents an alternative to model magnetic systems using a simpler, more physical approach. As the model is standard to other systems' models it allows the engineer or researcher to perform analogies among systems in order to gather insights and a clearer understanding of magnetic systems which up to now has been very complex and theoretical.

Artificial Magnetic Materials (AMMs) are a subgroup of metamaterials which are engineered to provide desirable magnetic properties not seen in natural materials. These artificial structures are designed to provide either negative or enhanced positive (higher than one) relative permeability. AMMs with negative permeability are used to develop Single Negative (SNG), or Double Negative (DNG) metamaterials. AMMs with enhanced positive permeability are used to provide magneto-dielectric materials at microwave frequencies where the natural magnetic materials fail to work efficiently. AMMs are realized by embedding metallic resonators in a host dielectric. These inclusions provide desirable magnetic properties near their resonance frequency. Artificial magnetic materials used as SNG, or DNG have many applications such as: sub-wavelength cavity resonators, sub-wavelength parallel-plate wave guides, sub-wavelength cylindrical and spherical core–shell systems, efficient electrically small dipole antennas, super lenses, THz active devices, sensitivity enhancement near-field probes using double and single negative media, and mutual coupling reduction between antennas. On the other hand, artificial magnetic materials used as magneto-dielectrics have other applications in developing enhanced bandwidth efficient miniaturized antennas, low profile enhanced gain antennas using artificial magnetic superstrates, wide band woodpile Electromagnetic Band Gap (EBG) structures, EBGs with enhanced in-phase reflection bandwidth used as artificial magnetic ground planes. In this thesis, several advances are added to the existing knowledge of developing artificial magnetic materials, in terms of analytical modeling, applications, realization, and experimental characterization. To realize AMMs with miniaturized unit cells, new inclusions based on fractal Hilbert curves are introduced, and analyzed. Analytical models, numerical full wave simulation, and experimental characterization are used to analyze, and study the new structures. A comprehensive comparison is made between the new inclusions, and perviously developed inclusions in terms of electromagnetic properties. The new inclusions have advantages of miniaturization, and less dispersion when compared to the existing structures in the literature. To realize multi-band AMMs, unit cells with multiple inclusions are proposed, designed, and analyzed. The new unit cells can be designed to give the desired magnetic properties either over distinguished multiple frequency bands, or over a single wide frequency band. Numerical full wave simulation is used to verify the proposed concept, and analytical models are provided for design, and optimization of the new unit cells. Unit cells with different configurations are optimized to get a wideband responce for the effective permeability. Space mapping technique is used to provide a link between analytically optimized structures, and full wave numerical simulation results. Two new methods are proposed for experimental characterization of artificial structures using microstrip, and strip line topologies. Using numerical results, the effect of anisotropy on the accuracy of the extracted parameters are investigated, and a fitting solution is proposed, and verified to address this challenge. New structures based on 2nd , and 3rd order fractal Hilbert curves are fabricated, and characterized using microstrip line, and strip line fixtures. Experimental results are presented, and compared with numerical results. The new experimental methods have advantages of lower cost, easier to fabricate and measure, and smaller sample size when compared to the existing methods in the literature. A new application is proposed for use of magnetic materials to develop wide band artificial magnetic conductors (AMC). Analytical models, and numerical analysis is used to validate the concept. A new ultra wideband AMC is designd, and analysed. The designed AMC is used as the ground plane to develop a low profile high gain ultra wide band antenna. The designed antenna is simulated, and its return loss, and gain is presented over a wide range of frequencies. A comprehensive study is presented on the performance of AMMs for the application of miniaturized antennas. A miniaturized antenna, using fractal Hilbert metamaterials as substrate, is fabricated, and measured. Measurement results are presented, and compared with numerical results. A parametric study is presented on the effect of the constitutive parameters of the artificial substrate on the performance of the miniaturized antenna. In this study, the effect of magnetic loss of AMM on the gain, and efficiency of the antenna, as well as the effect of dispersion of AMM on the bandwidth of the antenna is investigated.