Superparamagnetismo em Jacobsitas sintéticas
In this experimental study sintetic samples of Jacobsites (MnFe2O4) were synthesized by the Pechini method and calcined within ambient atmosphere and afterwards in the vacuum from 400 to 700ºC, the range of calcination temperatures. The X-Ray Diffraction (XRD) and the Scanning Electronic Microsco...
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superparamagnetismo Jacobsita espinélios MnFe2O4 superparamagnetism jacobsite spinels MnFe2O4 CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA |
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superparamagnetismo Jacobsita espinélios MnFe2O4 superparamagnetism jacobsite spinels MnFe2O4 CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA Barbosa, Mateus Bruno Superparamagnetismo em Jacobsitas sintéticas |
| description |
In this experimental study sintetic samples of Jacobsites (MnFe2O4) were synthesized
by the Pechini method and calcined within ambient atmosphere and afterwards in the
vacuum from 400 to 700ºC, the range of calcination temperatures. The X-Ray Diffraction
(XRD) and the Scanning Electronic Microscopy (SEM) analysis have shown that the samples
treated at 400ºC temperature are composed by a simple type of spinel phase, with a
crystallite size of 8:8nm for the sample calcined in ambient atmosphere and 20; 1nm for the
sample treated in the vacuum, showing that the cristallite average size can be manipulated
by the atmosphere control. The hysteresis loops for the sample calcined at 400ºC in ambient
atmosphere reveal features of superparamagnetic behavior with magnetization 29:3emu=g at
the maximum field of 1:2T. The sample calcined in 400oC under vacuum show magnetization
= 67emu=g at the maximum field of 1:5T. The sample treated at 500oC, under ambient
atmosphere, has shown besides the spinel phase, secondary phases of hematite (Fe2O3) and
bixbyite (FeMnO3). The hysteresis loops demonstrate a sharp drop of the magnetization
compared to the previous sample. The analysis has revealed that for the samples treated in
higher temperatures (600ºC and 700ºC) its observed the absence of the spinel phase and the
maintenance of the bixbyite and hematite. The hysteresis loops for those samples in accordance
to the external magnetic field are straight lines crossing the origin, consistent with the
antiferromagnetic behavior of the phases.The Mössbauer espectroscopy show to the sample
calcined at 400ºC within ambiente atmosphere two sextet and one doublet. The two sextets
are assigned to the hyperfine fields related to the magnetic deployment in the nuclei of Fe3+
ions, at the tetraedric and octaedric sites. The doublet is assigned to superparamagnetic
behavior of the particles with smaller diameter than dc . Now the sample calcined at 400ºC
under vacuum only show two sextet |
| author2 |
Araújo, José Humberto de |
| author_facet |
Araújo, José Humberto de Barbosa, Mateus Bruno |
| format |
masterThesis |
| author |
Barbosa, Mateus Bruno |
| author_sort |
Barbosa, Mateus Bruno |
| title |
Superparamagnetismo em Jacobsitas
sintéticas |
| title_short |
Superparamagnetismo em Jacobsitas
sintéticas |
| title_full |
Superparamagnetismo em Jacobsitas
sintéticas |
| title_fullStr |
Superparamagnetismo em Jacobsitas
sintéticas |
| title_full_unstemmed |
Superparamagnetismo em Jacobsitas
sintéticas |
| title_sort |
superparamagnetismo em jacobsitas
sintéticas |
| publisher |
Universidade Federal do Rio Grande do Norte |
| publishDate |
2015 |
| url |
https://repositorio.ufrn.br/jspui/handle/123456789/18600 |
| work_keys_str_mv |
AT barbosamateusbruno superparamagnetismoemjacobsitassinteticas |
| _version_ |
1773958304786022400 |
| spelling |
ri-123456789-186002017-11-02T16:32:53Z Superparamagnetismo em Jacobsitas sintéticas Barbosa, Mateus Bruno Araújo, José Humberto de http://lattes.cnpq.br/9234832358988109 http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4785558U2 Carriço, Artur da Silva http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4787041Z8 Soares, João Maria http://lattes.cnpq.br/2108722656012583 superparamagnetismo Jacobsita espinélios MnFe2O4 superparamagnetism jacobsite spinels MnFe2O4 CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA In this experimental study sintetic samples of Jacobsites (MnFe2O4) were synthesized by the Pechini method and calcined within ambient atmosphere and afterwards in the vacuum from 400 to 700ºC, the range of calcination temperatures. The X-Ray Diffraction (XRD) and the Scanning Electronic Microscopy (SEM) analysis have shown that the samples treated at 400ºC temperature are composed by a simple type of spinel phase, with a crystallite size of 8:8nm for the sample calcined in ambient atmosphere and 20; 1nm for the sample treated in the vacuum, showing that the cristallite average size can be manipulated by the atmosphere control. The hysteresis loops for the sample calcined at 400ºC in ambient atmosphere reveal features of superparamagnetic behavior with magnetization 29:3emu=g at the maximum field of 1:2T. The sample calcined in 400oC under vacuum show magnetization = 67emu=g at the maximum field of 1:5T. The sample treated at 500oC, under ambient atmosphere, has shown besides the spinel phase, secondary phases of hematite (Fe2O3) and bixbyite (FeMnO3). The hysteresis loops demonstrate a sharp drop of the magnetization compared to the previous sample. The analysis has revealed that for the samples treated in higher temperatures (600ºC and 700ºC) its observed the absence of the spinel phase and the maintenance of the bixbyite and hematite. The hysteresis loops for those samples in accordance to the external magnetic field are straight lines crossing the origin, consistent with the antiferromagnetic behavior of the phases.The Mössbauer espectroscopy show to the sample calcined at 400ºC within ambiente atmosphere two sextet and one doublet. The two sextets are assigned to the hyperfine fields related to the magnetic deployment in the nuclei of Fe3+ ions, at the tetraedric and octaedric sites. The doublet is assigned to superparamagnetic behavior of the particles with smaller diameter than dc . Now the sample calcined at 400ºC under vacuum only show two sextet Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Neste estudo experimental, amostras sintéticas de Jacobsitas (MnF e2O4) foram sintetizadas pelo método Pechini e calcinadas em atmosfera ambiente e em vácuo de 400 até 700ºC. Análises de difração de raio-x (DRX) e microscopia eletrônica de varredura (MEV) revelaram que a amostra calcinada em 400ºC é composta por uma fase simples tipo espinélio, com tamanho médio do cristalito de 8,8nm para amostra calcinada em atmosfera ambiente, e 20,1nm para amostra calcinada em vácuo, indicando que o tamanho médio do cristalito pode ser manipulado pelo controle da atmosfera. A curva de magnetização para amostra calcinada a 400ºC em atmosfera ambiente revela características de comportamento superparamagnético, com magnetização de 29:3emu=g num campo máximo de 1.2T . Já a amostra calcinada em 400ºC sob vácuo apresentou magnetização = 67emu/g no campo máximo de 1.5T . A amostra tratada em 500 ]C, em atmosfera ambiente, acusa além da fase espinélio, fases secundárias de hematita (Fe2O3) e bixbyita (FeMnO3). A curva de magnetização mostra uma queda abrupta na magnetização comparada com as amostras anteriores. A análise mostra que, para mais altas temperaturas (600ºC and 700ºC), observou-se apenas a continuação das fases hematita e bixbyita. A curva de magnetização dessas amostras são linhas retas cortando a origem, consistente com o comportamento antiferromagnético dessas fases. A espectroscopia Mössbauer revelou que para a amostra calcinada em 400ºC em atmosfera ambiente há dois sextetos e um dubleto. Os dois sextetos são atribuídos aos campos hiperfinos referentes ao desdobramento magnético no núcleo dos íons Fe3+, nos sítios tetraédricos e octaédricos. O dubleto é atribuído ao comportamento superparamagnético das partículas com diâmetro menor que dc. Já a amostra calcinada em 400ºC sob vácuo apresenta apenas dois sextetos. 2015-03-03T15:15:27Z 2015-02-26 2015-03-03T15:15:27Z 2012-03-27 masterThesis BARBOSA, Mateus Bruno. Superparamagnetismo em Jacobsitas sintéticas. 2012. 83 f. Dissertação (Mestrado em Física da Matéria Condensada; Astrofísica e Cosmologia; Física da Ionosfera) - Universidade Federal do Rio Grande do Norte, Natal, 2012. https://repositorio.ufrn.br/jspui/handle/123456789/18600 por Acesso Aberto application/pdf application/pdf Universidade Federal do Rio Grande do Norte BR UFRN Programa de Pós-Graduação em Física Física da Matéria Condensada; Astrofísica e Cosmologia; Física da Ionosfera |