Atenção: Todas as denúncias são sigilosas e sua identidade será preservada.
Os campos nome e e-mail são de preenchimento opcional
Metadados | Descrição | Idioma |
---|---|---|
Autor(es): dc.creator | Grave, Eddy de | - |
Autor(es): dc.creator | Costa, Geraldo Magela da | - |
Autor(es): dc.creator | Alboom, Antoine Van | - |
Autor(es): dc.creator | Vandenberghe, Robert Emile | - |
Data de aceite: dc.date.accessioned | 2019-11-06T13:33:21Z | - |
Data de disponibilização: dc.date.available | 2019-11-06T13:33:21Z | - |
Data de envio: dc.date.issued | 2015-04-09 | - |
Data de envio: dc.date.issued | 2015-04-09 | - |
Data de envio: dc.date.issued | 2013 | - |
Fonte completa do material: dc.identifier | http://www.repositorio.ufop.br/handle/123456789/4964 | - |
Fonte: dc.identifier.uri | http://educapes.capes.gov.br/handle/capes/557981 | - |
Descrição: dc.description | The heterosite phase occurring in a pegmatitic rock sample was characterized by X-ray diffraction, by energy-dispersive X-ray spectroscopy and by Mossbauer spectroscopy. The orthorhombic unit-cell parameters, expressed in A˚ , were found as a = 9.733 (1), b = 5.837 (1) and c = 4.776 (1). The composition was determined to be (Fe0.54Mn0.43Mg0.04)PO4. Mossbauer spectra recorded at temperatures T of 65K and higher consist of two broadened quadrupole doublets. Their isomer shifts ı are both diagnostic for the ferric state. The dominant doublet (∼60% of total area) exhibits an average quadrupole splitting _EQ,av of 1.62mm/s at room temperature, while the weaker broader doublet has _EQ,av = 0.68 mm/s. For temperatures T≤60K the spectra are composed of a broad sextet and a central quadrupole doublet. The doublet persists down to the lowest applied temperature of 17 K. It is concluded that this doublet is due to an Fe-bearing phase other than heterosite and which gives rise to the inner doublet appearing in the spectra recorded at T≥65 K. The broad sextets, attributable to the heterosite phase, were fitted with model-independent hyperfine-field distributions. However, it was consistently experienced that using the common Lorentzian-shaped elementary sextets composing the distribution, could not adequately reproduce the observed line shapes. Instead, the calculations had to be based on the diagonalization of the complete hyperfine-interaction Hamiltonian. This is due to the unusually strong quadrupole interaction. The as-such calculated hyperfine parameters of the heterosite phase at 17K may be summarized as follows: maximum-probability hyperfine field Bhf,m = 473 kOe, isomer shift ıFe = 0.54 mm/s, average quadrupole coupling constant ½e2qQ = 1.50 mm/s, asymmetry parameter of the EFG _ = 0.80, and polar angles of the hyperfine field with respect to the EFGs principal axes frame˝=40◦ and _ =90◦. The temperature variation of the hyperfine field was interpreted in terms of the Bean–Rodbell (BR) model. The BR parameter, _BR, was found to be 0.90, indicating a first-order magnetic transition at TN = 59.7 K. The temperature variation of the isomer shift is explained by the second-order Doppler shift ıSOD. Using the Debye model for the lattice vibrational spectrum for calculating ıSOD, the characteristic Mossbauer temperature _M was found to be 400 K, which is unusually low for a ferric compound. | - |
Idioma: dc.language | en | - |
Direitos: dc.rights | O Periódico Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy concede permissão para depósito deste artigo no Repositório Institucional da UFOP. Número da licença: 3577160256613. | - |
Palavras-chave: dc.subject | Mössbauer spectroscopy | - |
Palavras-chave: dc.subject | Heterosite | - |
Palavras-chave: dc.subject | Magnetic hyperfine field | - |
Palavras-chave: dc.subject | Isomer shift | - |
Título: dc.title | Low-temperature Mossbauer study of heterosite, (Fe, Mn)PO4. | - |
Aparece nas coleções: | Repositório Institucional - UFOP |
O Portal eduCAPES é oferecido ao usuário, condicionado à aceitação dos termos, condições e avisos contidos aqui e sem modificações. A CAPES poderá modificar o conteúdo ou formato deste site ou acabar com a sua operação ou suas ferramentas a seu critério único e sem aviso prévio. Ao acessar este portal, você, usuário pessoa física ou jurídica, se declara compreender e aceitar as condições aqui estabelecidas, da seguinte forma: