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I performed first principles studies of the site occupancy and magnetic properties of zinc-tin-substituted strontium hexaferrite by using density functional theory. In this study, I determined the site preference of zinc and tin atoms when they are restricted to occupy the same sublattice in strontium-hexaferrite. I found that Zn and Sn atoms prefer to replace Fe ions at 2a sublattice under this restriction and caused the saturation magnetization to decrease.

Il existe actuellement un important besoin en dispositifs électroniques dans le domaine des longueurs d’ondes millimétriques, tels que les circulateurs et les isolateurs fonctionnant dans la gamme de fréquence 30-100 GHz. Les aimants permanents qui garantissent la propagation de l’onde électromagnétique dans ces dispositifs comportent très généralement des éléments terres rares. En raison du coût à l’acquisition de ces éléments, d’une part, ainsi que de leur coût environnemental d’autre part, il existe une demande d’aimants permanents produits sans terres rares. Les ferrites durs peuvent présenter les propriétés demandées pour une intégration dans les dipositifs micoondes non réciproques. Ainsi, les particules de ferrite de baryum (BaM) possèdent un champ d’anisotropie magnétocristallin important, dirigé selon l’axe de facile aimantation. Un matériau autopolarisé, constitué d’un empilement de ces particules, peut donc présenter une aimantation permanente d’intensité suffisante pour les applications visées. De nombreuses méthodes d’élaboration de tels matériaux ont été mises au point. Cependant les mises en oeuvre de ces méthodes sont contraignantes. En revanche, nous avons mis au point dans le présent travail un processus de réalisation de ferrites de BaM massifs autopolarisés, dont l’aspect technologique est simple (basé sur des méthodes de chimie douce et des traitements thermiques adaptés), et très abordable financièrement. Les résultats obtenus sont très compétitifs (aimantation rémanente normalisée MR/MS comprise entre 0.87 et 0.90. Le champ coercitif HC atteint la valeur de 303 kA/m, rendant le matériau peu sensible aux effets démagnétisants), et permettent d’envisager la production de ces matériaux en vue d’applications à des fréquences allant jusqu’à 55 GHz. / Presently, there is a critical need for millimeter wave devices, among which are non-reciprocal devices such as isolators and circulators, which operate in the frequency range from about 30 GHz to 100 GHz.Permanent magnets that ensure the propagation of the wave in such devices are for long based on rare-earth elements. Nowadays, the escalation of rare earths cost encourages to look for alternative materials containing much less, or no, rare earth elements selected from the most common and most available. Alternatively, hard ferrites may show the required potential for integration into non-reciprocal microwave devices. Barium ferrite (BaM) is a wellknown, high-performance, permanent magnet material with a large magneto-crystalline anisotropy along the c-axis of its hexagonal structure. A suitable form of barium ferrite for mm-wave applications is a magnetically oriented bulk material.Several constraining processing techniques were therefore set up to perform the alignment and compaction of plate hexaferrite particles. In contrast to these methods, the present study demonstrates the feasibility of simple alternative ways to provide highly oriented bulk compacts made of BaM particles. In the present work efficient and inexpensive chemical processes (co-precipitation, dry mixing and wet mixing) are presented that produces highly oriented bulk compacts made of Barium hexaferrites (BaM) particles. Hysteresis loops that display very competitive squarenesses between 0.87 and 0.90 (normalized remanent magnetization) and coercivity as high as 303 kA/m are obtained. The sensitivity to demagnetizing effects is therfore reduced. These properties make these BaM bulk ferrite materials suitable for selfbiased applications at frequencies up to 55 GHz.

Ces travaux de thèse consistent à élaborer des nanocomposites Polyaniline/hexaferrite pour l’absorption des micro-ondes. L’idée principale est la mise en œuvre de matériaux composites à base de polymères conducteurs intrinsèques telle la Polyaniline que nous avons dopée avec différents types d’acides (HCl, CSA, NSA et TSA…) et l’hexaferrite de baryum de type magnétoplombite (M) stœchiométrique ou substitué. Au niveau de l’hexaferrite de baryum, la substitution du Fe3+ s’est faite par les ions Al3+, Bi3+, Cr3+ et Mn3+.L’hexaferrite de baryum et les hexaferrites substitués par les différents ions cités ci-dessus ont été synthétisés par voie hydrothermale dynamique en faisant varier divers paramètres au cours de la synthèse (pH, température, temps, rapport [OH-]/[NO3-]…).L’élaboration des composites Polyaniline/hexaferrite (pur ou substitués) a été effectuée par polymérisation oxydative en utilisant plusieurs techniques de synthèse : la polymérisation chimique en solution (en tenant compte de la nature de l’acide utilisé) avec ou sans agitation (Aqueous-Based Polymerization with or without stirring) et la polymérisation oxydative par voie solide (Solid-Based Polymerization). L’optimisation de ces différentes techniques de synthèse après caractérisations physicochimiques (DRX, FTIR, ATG, MEB, EDX), diélectriques (ε’, ε’’, σdc) et magnétiques (Mr, Ms, Hc, Tc, µ’, µ’’) des échantillons, a montré que la polymérisation par voie solide se trouve la méthode la plus facile, économique et respectueuse de l’environnement. Elle est aussi adaptée à la production du composite Pani/BaFe12O19 avec de bonnes propriétés structurales, physiques et magnétiques. L’étude de la substitution du Fe3+ dans le BaFe12O19 par Al3+, Bi3+, Cr3+ et Mn3+ a montré une forte dépendance des propriétés structurales et magnétiques avec la distribution de ces ions dans la maille cristalline hexagonale. En effet, les ions Al3+, Cr3+ et Mn3+ ont une tendance à occuper les sites tétraédriques, alors que le Bi3+ occupe les sites octaédriques. Une augmentation de Hc associée à la taille des cristallites a été observée pour les particules substituées avec l'Al et le Cr alors qu’une modification de l'anisotropie magnetocristalline (fort terme d'ordre supérieur) a été mise en évidence pour les substitutions Bi et Mn, dû à leur grand rayon ionique. L’incorporation des hexaferrites substitués dans la Polyaniline pour obtenir des composites Pani/BaMeFe11O19, où Me = Al, Bi, Cr et Mn, révèle une variation des propriétés électromagnétiques dans la gamme de fréquences allant de 1 à 18 GHz. En effet, ces variations sont dues à la formation de dipôles entre l’ion de substitution et les cations O2- dans le ferrite qui sont responsables de la résonance ferromagnétique, de l'anisotropie magnétocristalline et des interactions avec la matrice polymérique. Le composite Pani/BaFe12O19 présente des absorptions dans la bande X qui se déplacent vers la bande Ku avec la substitution du fer confirmant / This thesis deals with the formulation of Polyaniline/hexaferrite nanocomposite for absorbing electromagnetic waves. The main idea is the process of composite materials based on polymers intrinsic conductors such as polyaniline that we doped with different types of acids (HCl, CSA, NSA, and ... TSA) and barium hexaferrite with magnetoplumbite structure with or without substitution according to desired stoichiometries. In the barium hexaferrite, the substitution of Fe 3+ is made by Al3+, Bi3+, Cr3+ and Mn3+ ions.The barium hexaferrite and its substitutions by different ions mentioned above were synthesized dynamic hydrothermal method by varying various parameters during the synthesis (pH, temperature, time, ratio [OH-]/[NO3-] ...).The elaboration of polyaniline/hexaferrite composite (pure or substituted) was carried out by oxidative polymerization using various synthesis techniques: Aqueous-Based Polymerisation with or without agitation (taking into account the nature of the acid used) (ABP) and Solid-Based Polymerization (SBP). The optimization of these various synthesis techniques after physicochemical (XRD, FTIR, TGA, SEM, EDX), dielectric (ε ', ε' ', σdc) and magnetic (Mr, Ms, Hc, Tc, µ', µ'') characterizations of the samples showed that the solid route is the easiest method, economical and environmentally friendly. It is also suitable for the production of composite Pani/BaFe12O19 with good structural, physical and magnetic properties.The study of the substitution of Fe 3+ in the BaFe12O19 by Al3+, Bi3+, Cr3+ and Mn3+ showed a strong dependence of the structural and magnetic properties with the distribution of these ions in the hexagonal crystal lattice. In fact, Al3+, Cr3+ and Mn3+ ions tend to occupy the tetrahedral sites, while the Bi3+ favoured the octahedral sites. An increase in Hc associated with the small crystallite size observed for particles substituted with Al and Cr and the enhancement magnetocristalline anisotropy (strong higher order term) for Bi and Mn due to their high ionic radius.The incorporation of the substituted hexaferrite in the polyaniline to obtain Pani/BaMeFe11O19 composite, where Me = Al, Bi, Cr and Mn, reveals a variation in electromagnetic properties in the frequency range from 1 to 18 GHz. In fact, these variations are due to the formation of dipoles between the substituting ion and surrounding O2- cations in the ferrite which are responsible for the ferromagnetic resonance, the magnetocrystalline anisotropy and the exchange interaction with the polymer. The composite Pani/BaFe12O19 shows absorption bands at the X-band that shift to the Ku-band with the substitution of iron, confirming the potential of these materials for microwave applications.

Submitted by Simone Souza (simonecgsouza@hotmail.com) on 2018-04-23T15:02:49Z No. of bitstreams: 1 DISS_2015_ João Roberto Sousa de Miranda.pdf: 2803422 bytes, checksum: ed72f32ed8bf4bb40f39ed7aec7cb49b (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2018-05-14T17:13:38Z (GMT) No. of bitstreams: 1 DISS_2015_ João Roberto Sousa de Miranda.pdf: 2803422 bytes, checksum: ed72f32ed8bf4bb40f39ed7aec7cb49b (MD5) / Made available in DSpace on 2018-05-14T17:13:38Z (GMT). No. of bitstreams: 1 DISS_2015_ João Roberto Sousa de Miranda.pdf: 2803422 bytes, checksum: ed72f32ed8bf4bb40f39ed7aec7cb49b (MD5) Previous issue date: 2015-04-10 / CAPES / O presente trabalho trata das propriedades dielétricas, estruturais e morfológicas da hexaferritas Ba2Co2Fe12O22 (Co2Y) com adição de 0,25; 0,50; 0,75 e 1,00% de Óxido de Vanádio (V2O5), durante a sua realização os pós da mistura foram produzidos a partir da reação de estado sólido ou método cerâmico tradicional. Os registros coletados apontam que nas últimas décadas as cerâmicas magnéticas (hexaferritas) tem se consolidado como materiais cerâmicos com forte atrativo para uso em dispositivos eletrônicos que necessitam de grande eficiência, lembrando que as principais vantagens oferecidas por essas cerâmicas são possibilidade de miniaturização ou compactação e baixo custo de fabricação, além de serem constituídas de materiais leves e termicamente estáveis. É fundamental mencionar que as ferritas se destacam por apresentarem alta e constante dielétrica e baixa perda dielétrica o que desperta grande interesse na indústria de telecomunicações, e após a calcinação, as amostras foram dopadas e maceradas em um cadinho, em seguida foram conformadas em prensas para que fossem obtidas amostras em forma de pastilhas cilíndricas. O método utilizado para a análise estrutural das amostras foi realizado por meio da técnica de difração de raios-X e o estudo morfológico foi realizado por meio da análise visual da microscopia eletrônica de varredura onde se pôde comprovar a relação entre as microestruturas e as densidades das amostras obtidas através do método de Arquimedes. A pesquisa tem como a caracterização dielétrica que ocorre no range de frequência de 1 Hz a 1 MHz e intervalo de temperatura de 30°C a 200°C com a finalidade de se obter e analisar material cerâmico com possível aplicação em dispositivos eletrônicos. O estudo registra que o objetivo inicial da pesquisa era se obter um material de constante dielétrica alta, com baixa perda dielétrica e estabilidade térmica. / The present work treat dielectric, structural and morphological properties of hexaferritas Ba2Co2Fe12O22 (Co2Y) with addition of the 0,25; 0,50; 0,75 e 1,00% of the Vanadium Oxide (V2O5), during its mixing powders embodiment were produced from the solid state reaction method or ceramic traditional. The records collected point out that in recent decades the magnetic ceramics ((hexaferrites) It has been established as ceramic materials with strong attractive for use in electronic devices that require high efficiency, noting that the main advantages offered by these ceramics are possibility of miniaturization or compactness and low cost manufacturing, besides being formed of lightweight materials and thermally stable. It is essential to mention that the ferrites stand out because they have high dielectric constant and low dielectric loss and which arouses great interest in the telecommunications industry, and after calcination, the samples were doped and macerated in a crucible, they were then formed into samples which presses were obtained in the form of cylindrical pellets. The method used for structural analysis of samples was performed by means of diffraction technique of X ray and the morphological study was carried out through visual scanning electron microscopy analysis where it could prove the relationship between microstructure and densities of the samples obtained by Archimedes method. . Research has dielectric characteristics as occurring in the frequency range since 1 Hz to 1 MHz and temperature range 30°C to 200°C in order to obtain and analyze ceramic material with potential application in electronic devices. The study notes that the initial objective of the research was to obtain a high dielectric constant material with low dielectric loss and thermal stability.

Hexaferrites have a broad scope for application based on their physical properties. To study the influence of replacing cerium and gadolinium ions in hexaferrites, it is very important to understand their structural, electrical, and magnetic properties of hexaferrites. In this regard, the W-type strontium hexaferrite doped with Ce3 + and Gd3+ ions was prepared using a proteic sol-gel process under a pressure of 3000 psi and sintered at 1200º C for 2 h at a heating rate of 1 and 2º C/min. A pure W-type strontium hexaferrite was identified using X-ray diffraction (XRD); the XRD patterns exhibited increasing lattice parameters and unit cell volume as a function of doping. Scanning electron microscopy analysis indicated growth on plates with hexagonal divisions. The inserted Gd3+ and Ce3+ ions caused imbalance in the lattice. Therefore, some of the Fe3+ ions present in the octahedral site were converted to Fe2+ ions. Thus, the Curie temperature was reduced to 474º C, increasing the coercivity and reducing the superexchange interactions between Fe-O. The high saturation magnetization and low coercivity in the samples indicate that the hexaferrites are potential candidates for applications involving microwave absorption. In addition, impedance spectroscopy measurements indicated the presence of a replacement threshold with rare earth ions, which results in an increased resistivity; this is predominantly mediated by oxygen vacancies in the Ce3+-doped hexaferrite. / As hexaferritas apresentam um vasto campo de aplicações a depender de suas propriedades físicas. Estudar a influência da substituição dos íons de cério e gadolínio é de suma importância para entender como funciona o mecanismo de obtenção das propriedades estruturais, elétricas e magnéticas nas hexaferritas. Dessa forma, a hexaferrita de estrôncio tipo W foi dopada com íons de Ce3+ e Gd3+ foi obtida via processo sol-gel proteico à 3000 psi e sinterizada a 1200º C/2h com taxa de aquecimento de 1 e 2 /C/min. A fase pura da hexaferrita de estrôncio tipo W foi identificada por difração de raios X com aumento dos parâmetros de rede e volume da cela unitária em função da dopagem. As análises de microscopia eletrônica de varredura indicam o crescimento em placas com clivagens hexagonais. . Os íons de Gd3+ e Ce3+ quando inseridos provocou um desbalanceamento de cargas, levando a transformação de certa quantidade de íons Fe3+, presente no sítio octaédrico, para Fe2+. Tal fato leva a redução da temperatura de Curie para 474º C, aumento da coercividade e redução das interações de super troca entre Fe-O. A alta magnetização de saturação e baixa coercividade apresentadas pelas amostras, indicam que as hexaferritas são considerados candidatos em potencial para fins de absorção de micro-ondas. Além disso, as medidas de espectroscopia de impedância indicam que existe um limiar de substituição com os íons terra rara para que haja aumento da resistividade e a condução ocorra predominantemente mediada por vacâncias de oxigênio na hexaferrita dopada com íon de Ce3+. Palavras

This dissertation investigates how the magnetic properties of strontium hexaferrite change upon the substitution of foreign atoms at the Fe sites. Strontium hexaferrite, SrFe12O19 is a commonly used hard magnetic material and is produced in large quantities (around 500,000 tons per year). For different applications of strontium hexaferrite, its magnetic properties can be tuned by a proper substitution of the foreign atoms. Experimental screening for a proper substitution is a cost-intensive and time-consuming process, whereas computationally it can be done more efficiently. We used the ‘density functional theory’ a first principles based method to study substituted strontium hexaferrite. The site occupancies of the substituted atoms were estimated by calculating the substitution energies of different configurations. The formation probabilities of configurations were used to calculate the magnetic properties of substituted strontium hexaferrite. In the first study, Al-substituted strontium hexaferrite, SrFe12-xAl x O19, with x = 0.5 and x = 1.0 were investigated. It was found that at the annealing temperature the nonmagnetic Al+3 ions preferentially replace Fe+3 ions from the 12k and 2a sites. We found that the magnetization decreases and the magnetic anisotropy field increases as the fraction, x of the Al atoms increases. In the second study, SrFe12-x Gax O19 and SrFe12-x Inx O19 with x = 0.5 and x = 1.0 were investigated. In the case of SrFe12-x Gax O19, the sites where Ga+3 ions prefer to enter are: 12k, 2a, and 4f1. For SrFe12-x Inx O19, In+3 ions most likely to occupy the 12k, 4f1, and 4f2 sites. In both cases the magnetization was found to decrease slightly as the fraction of substituted atom increases. The magnetic anisotropy field increased for SrFe12-x Gax O19, and decreased for SrFe12-x Inx O19 as the concentration of substituted atoms increased. In the third study, 23 elements (M) were screened for their possible substitution in strontium hexaferrite, SrFe12-x Mx O19 with x = 0.5. In each case the site preference of the substituted atom and the magnetic properties were calculated. We found that Bi, Ge, Sb, Sn, and Sc can effectively increase the magnetization, and Cr, P, Co, Al, Ga, and Ti can increase the anisotropy field when substituted into strontium hexaferrite.

Dans son ensemble, cette thèse porte sur la synthèse, l’étude structurale et l’étude des propriétés magnétiques et de transport de différentes familles d’oxydes de ruthénium, présentant des comportements électroniques et magnétiques variés, de structure rutile, hexaferrite de type R et hollandite. Le but de ce travail était l’étude des particularités des oxydes de ruthénium sondées par l’effet Seebeck dans les matériaux suivants : RuO2 de structure rutile (chaînes d’octaèdres de RuO6 liés par leurs arêtes, interconnectées par leurs sommets) à transport de type Boltzmann dominé par les interactions électron-phonon, les hexaferrites de type R BaCo2Ru4O11 et BaMn2Ru4O11 (octaèdres de RuO6 liés par les arêtes, formant des plans kagomé, et octaèdres de RuO6 liés par une face) ferromagnétiques doux et mauvais métaux, et deux nouvelles hollandites Sr1.5Ru6.1Cr1.9O16 et Ba1.5Ru6.1Cr1.9O16 (doubles chaînes de RuO6 liés par les arêtes, interconnectées par les sommets) avec agglomérats de spins localisés. La synthèse de ces deux nouvelles hollandites par réaction à l’état solide a permis de mettre en évidence l’existence de magnétorésistance négative dans cette famille de composés. Cette thèse montre que le comportement du coefficient Seebeck S d'oxydes de ruthénium à structures constituées d'octaèdres RuO6 majoritairement liés par leurs arêtes présente deux comportements différents. À basse T, S dépend fortement de la structure cristallographique et de la structure électronique associée. Par contre, dans la limite haute T, S tend vers une valeur commune indépendamment de la structure comme rapporté ici pour les hexaferrites de type R et les hollandites, et comme observé précédemment dans la pérovskite SrRuO3 (octaèdres RuO6 liés par les sommets) ferromagnétique métallique et dans la quadruple pérovskite LaCu3Ru4O12 (octaèdres RuO6 liés par les sommets) métallique présentant un magnétisme de type Pauli. Dans ces hexaferrites de type R BaCo2Ru4O11 et BaMn2Ru4O11 et dans ces deux nouvelles hollandites Sr1.5Ru6.1Cr1.9O16 et Ba1.5Ru6.1Cr1.9O16, le coefficient Seebeck à haute température atteint une valeur dominée par l’entropie de spin du ruthénium. / This thesis deals with the synthesis, the structural study and the magnetic properties and electronic transport studies of different ruthenium oxide families, presenting various magnetic and electronic behaviors, with rutile, R-type hexaferrite and hollandite structures. The goal of this thesis was the study of the ruthenium oxide peculiarities probed by the Seebeck effect in the following materials: RuO2 rutile (edge-shared RuO6 chain interconnected by their vertices) with Boltzmann type transport dominated by electron-phonon interactions, BaCo2Ru4O11 et BaMn2Ru4O11 R-type hexaferrites (edge-shared RuO6 octahedra, forming kagome planes, and face-shared RuO6 octahedra) soft ferromagnetic bad metals, and two new hollandites Sr1.5Ru6.1Cr1.9O16 et Ba1.5Ru6.1Cr1.9O16 (double chains of edge-shared RuO6 octahedra, interconnected by their vertices) with localized transport and cluster-glass behavior. The synthesis of both new hollandites by solid state reaction allowed us to show the existence of negative magnetoresistance in this compound family. This thesis shows that the behavior of the Seebeck coefficient of ruthenium oxides with structures mainly consisting of edge-shared RuO6 octahedra presents two different behaviors. At low T, S strongly depends on the crystallographic structure and on the associated electronic structure. On the other hand, in the high T limit, S tends a common value independently of the structure as reported here for the R-type hexaferrites and the hollandites and as previously observed in the ferromagnetic metal SrRuO3 perovskite (apex-shared RuO6 octahedra) and in the metallic with Pauli-type magnetism quadruple perovskite LaCu3Ru4O12 (apex-shared RuO6 octahedra). In these R-type hexaferrites BaCo2Ru4O11 and BaMn2Ru4O11 and these two new hollandites Sr1.5Ru6.1Cr1.9O16 and Ba1.5Ru6.1Cr1.9O16, the high temperature Seebeck coefficient reaches a value dominated by the Ru spin entropy term.

M-type barium hexaferrite powders doped with titanium and/or cobalt have been synthesized according to the stochiometric formulations BaFe(12 &amp / #8211 / (4/3)x)TixO19, BaFe12-xCoxO19 , BaFe12-2xTixCoxO19 (x varying from 0 to 1.5 with an increment of 0.5) by the mixed oxide approach. The powders were used to manufacture small ceramic tiles by sintering each composition at 1250 &deg / C with soaking times ranging from 1 to 16 hours. XRD work revealed formation of the magnetoplumbite crystal structure in all ceramics. The variations in processing parameters led to differences in microstructure and various dielectric and magnetic properties of the ceramic tiles. The interaction of the ceramics with electromagnetic waves was characterized by using a vector network analyzer in the X and Ku bands. The results revealed that, undoped barium hexaferrite ceramics and those doped with low titanium exhibited good microwave absorption properties.

Made available in DSpace on 2014-12-17T14:06:54Z (GMT). No. of bitstreams: 1 SheilaBG_DISSERT.pdf: 1652158 bytes, checksum: ad653b0a72284122fdd7e2e051380eb2 (MD5) Previous issue date: 2010-04-23 / Universidade Federal do Rio Grande do Norte / In this study barium hexaferrite was (general formulae BaFe12O19) was synthesized by the Pechini method under different conditions of heat treatment. Precursors like barium carbonate and iron nitrate were used. These magnetic ceramic, with magnetoplumbite type structure, are widely used as permanent magnet because of its excellent magnetic properties, such as: high Curie temperature, good magnetic anisotropy, high coercivity and corrosion resistance. The samples were characterized by thermal analysis (DTA and TG), X- ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) end Vibrating sample Magnetometer (VSM). The results confirm the expected phase, which was reinforced according to our analysis. A single phase powder at relatively high temperatures with particle sizes around 100 nm was obtained. The characteristic magnetic behavior one of the phases has been noted (probably superparamagnetic material), while another phase was identified as a ferrimagnetic material. The ferrimagnetic phase showed vortex configuration with two central and slightly inclined plateaus. In general, increase of heat treatment temperature and time, directly influenced the technological properties of the samples / Neste trabalho foi sintetizado o composto da Hexaferrita de B?rio de f?rmula geral BaFe12O19, preparado pelo m?todo Pechini (sob diferentes condi??es de tratamento t?rmico), utilizando-se como precursores o carbonato de b?rio e o nitrato de ferro. Estes materiais cer?micos magn?ticos, com estrutura do tipo magnetoplumbita, s?o amplamente utilizados como magnetos permanentes, devido as suas excelentes propriedades magn?ticas, tais como: alta temperatura de Curie, boa anisotropia magn?tica, alta coercividade e resist?ncia ? corros?o. As amostras obtidas foram caracterizadas pelas t?cnicas: An?lises T?rmicas (DTA e TG), Difra??o de raios-X (DRX), Espectroscopia de absor??o na regi?o do infravermelho (FTIR), Microscopia Eletr?nica de Varredura (MEV) e Magnet?metro Vibracional (VSM). Os resultados mostraram a fase desejada, onde foi intensificada de acordo com as an?lises realizadas, resultando na obten??o de um p? monof?sico nas temperaturas relativamente altas com tamanhos de part?culas em torno de 100 nm. Os materiais possuem fases de comportamento magn?tico caracter?stico, provavelmente de um material superparamagn?tico e outro ferrimagn?tico que em temperaturas mais elevadas apresentaram uma configura??o de v?rtice, com dois plat?s centrais com pequenas inclina??es. De modo geral, os aumentos da temperatura de tratamento t?rmico e do tempo, influenciaram diretamente nas propriedades tecnol?gicas das amostras