Characterization of a natural magnetite |
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| Authors: | A C Doriguetto N G Fernandes A I C Persiano E Nunes Filho J M Grenèche J D Fabris |
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| Institution: | (1) Departamento de Química, ICEx, UFMG, 31270-901 Belo Horizonte, MG, Brazil e-mail: dorigue@if.sc.usp.br Tel.: +55-16-2739887 Fax: +55-16-2739881, BR;(2) Departamento de Física, ICEx, UFMG, 31270-901 Belo Horizonte, MG, Brazil, BR;(3) Departamento de Física, UFES, 29069-900 Vitória, ES, Brazil, BR;(4) Laboratoire de Physique de L'Etat Condensé, UMR CNRS 6087, Université du Maine, 72085 Le Mans Cedex 9, France, FR |
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| Abstract: | Single crystals of a rock magnetite were separated from steatite cobbles collected in a geological site near the city of Serro (18° 36′ 47′′ S 43° 22′ 46′′ W), Minas Gerais, Brazil. A typically well-shaped magnetite single crystal was characterized by chemical analysis, 57Fe Mössbauer spectrometry at 300, 77 and 4 K and under an applied magnetic field of 6 T at 10 K, magnetization measurements and electronic microprobe. From Mössbauer data, the sample is stoichiometric with a tetrahedral and octahedral site occupancy ratio of 1:2. Elemental chemical analysis and point-to-point electron microscope probing show some inclusions of lamellar ilmenite (≤ 1 mass%) randomly distributed throughout the magnetite matrix, and also that the magnetite matrix is constituted only by Fe2+ and Fe3+, with no isomorphic substitution. Results are discussed on the basis of the magnetization curve and of the temperature dependence of the AC magnetic susceptibility. The Verwey transition occurs in the temperature range of 100–115 K, observed by a sudden change in the temperature dependence of the magnetization. |
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| Keywords: | M?ssbauer spectroscopy Cation distribution Magnetic properties Steatite Spinel |
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