Estudo de síntese e caracterização em sistemas magnéticos de estrutura do tipo espinélio: NiMn2O4 e CoMn2O4
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Data
2010-07-29
Autores
Ferreira, Rafael Aparecido [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Materiais óxidos avançados com composição nominal Ni'Mn IND. 2''O IND. 4' e Co'Mn IND. 2''O IND. 4' obtidos pelo métodos dos precursores poliméricos foram tratados termicamente em diferentes temperaturas ('800 GRAUS'C /4h e '1000 GRAUS'C/16h) com a finalidade de obter um material monofásico, condição essa ideal para o estudo das propriedades cristalográficas, estruturais e magnéticas destes compostos. A obtenção de materiais monofásicos é importante para uma melhor interpretação das suas propriedades magnéticas. o método dos precursores poliméricos permitiu obter amostras com quantidades mínimas de fases secundárias, confirmadas por difração de raios X e refinamento estrutural pelo método de Rietveld. As medidas de magnetização indicam que tanto as amostras Ni'Mn IND. 2''O IND. 4' e Co'Mn IND. 2''O IND. 4' apresentam uma competição entre duas subredes, uma com resposta ferromagnética, e outra com resposta antiferromagnética e isso deve se a ocupação dos cátions dentro dos sítios tetraédricos e octaédricos do espinélio. Para a determinação das fases do Ni'Mn IND. 2''O IND. 4' e do Co'Mn IND. 2''O IND. 4', foi utilizada a técnica de difração de raios X (DRX), a qual mostra a formação de duas fases para a composição Ni'Mn IND. 2''O IND. 4': uma fase predominante de Ni'Mn IND. 2''O IND. 4' (ICSD-9403) com estrutura cúbica do tipo espinélio e uma fase secundária de NiO (COD 9008693) arranjada em estrutura do tipo cúbica. Já a composição Co'Mn IND. 2''O IND. 4' se cristaliza como um espinélio cin sistema tetragonal (JCPDS - 77-0471) como fase principal. Para os estudos do comportamento magnético das amostras foram realizadas medidas magnéticas com procedimento ZFC-FC de 10 k a 300 com campos aplicados de 100 Oe, 500 Oe and 1 kOe. Para um campo aplicado de 100 Oe a amostra de Ni'Mn IND. 2''O IND. 4' exibe uma resposta antiferromagnética na...
Advanced oxide materials with nominal composition Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' obtained by polymeric precursors method was heat-treated at different temperatures ('800 GRAUS'C/4h and '1000 GRAUS'C/16h) in order to obtain a single-phase material, being the ideal condition for the magnetic measurements and structural refinement by the Rietveld method to be performed. In order to obtain single-phase materials is important to better explaining the magnetic behavior of the sample. The polymeric precursor method allowed obtaining samples with minimal amounts of secundary phase, confirmed by X-ray difraction technique and structural refinement by the Rietveld method. The magnetic measurements indicate that the samples Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' presents a competition between ferromagnetic and antiferromagnetic respondes for the different magnetic sublattice, this should be the occupation in the tethahedral and octahedral sites of spinel. For the determination of the Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' phases, was used XRD technique, which showed the formation of two phases for the composition Ni'Mn IND. 2''O IND. 4: a predominant phase Ni'Mn IND. 2''O IND. 4' (ICSD-9403) with spinel arranged in a cubic system and a secondary phase of NiO (COD 9008693) with cubic type structure. Otherwise, the Co'Mn IND. 2''O IND. 4' composition showed the crystallization in a tetragonal system (JCPDS - 77-0471), as a main crystallographic phase. Magnetization curves were obtained as a function of the temperature in ZFC-FC procedure in magnetic fields of 100 Oe, 500 Oe and 1 KOe. For a field applied of 100 Oe the sample showed an antiferromagnetic response in the ZFC curve, while in the FC curve a ferromagnetic behavior can be observed for the Ni'Mn IND. 2''O IND. 4' composition. Magnetization curves showed ferromagnetic ... (Complete abstract click electronic access below)
Advanced oxide materials with nominal composition Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' obtained by polymeric precursors method was heat-treated at different temperatures ('800 GRAUS'C/4h and '1000 GRAUS'C/16h) in order to obtain a single-phase material, being the ideal condition for the magnetic measurements and structural refinement by the Rietveld method to be performed. In order to obtain single-phase materials is important to better explaining the magnetic behavior of the sample. The polymeric precursor method allowed obtaining samples with minimal amounts of secundary phase, confirmed by X-ray difraction technique and structural refinement by the Rietveld method. The magnetic measurements indicate that the samples Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' presents a competition between ferromagnetic and antiferromagnetic respondes for the different magnetic sublattice, this should be the occupation in the tethahedral and octahedral sites of spinel. For the determination of the Ni'Mn IND. 2''O IND. 4' and Co'Mn IND. 2''O IND. 4' phases, was used XRD technique, which showed the formation of two phases for the composition Ni'Mn IND. 2''O IND. 4: a predominant phase Ni'Mn IND. 2''O IND. 4' (ICSD-9403) with spinel arranged in a cubic system and a secondary phase of NiO (COD 9008693) with cubic type structure. Otherwise, the Co'Mn IND. 2''O IND. 4' composition showed the crystallization in a tetragonal system (JCPDS - 77-0471), as a main crystallographic phase. Magnetization curves were obtained as a function of the temperature in ZFC-FC procedure in magnetic fields of 100 Oe, 500 Oe and 1 KOe. For a field applied of 100 Oe the sample showed an antiferromagnetic response in the ZFC curve, while in the FC curve a ferromagnetic behavior can be observed for the Ni'Mn IND. 2''O IND. 4' composition. Magnetization curves showed ferromagnetic ... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Quimica - Síntese, Magnetismo, Fase espinélio, Chemical Synthesis, Rietveld refinament, Spinel, Magnetism
Como citar
FERREIRA, Rafael Aparecido. Estudo de síntese e caracterização em sistemas magnéticos de estrutura do tipo espinélio: NiMn2O4 e CoMn2O4. 2010. 89 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências, 2010.