| Natural magnetite nanoparticles from an iron-ore deposit: size dependence on magnetic properties Auteur(s) : Rivas-Sanchez, M. L. Alva-Valdivia, L. M. Arenas-Alatorre, J. Urrutia-Fucugauchi, J. Perrin, Mireille Goguitchaichvili, A. Ruiz-Sandoval, M. Molina, M. A. R. Auteurs secondaires : Laboratorio de Paleomagnetismo, Instituto de Geofísica, Universidad Nacional Autónoma de México ; Université du Québec Instituto de Física, Universidad Nacional Autónoma de México ; Université du Québec Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Laboratorio Interinstitucional de Magnetismo Natural, Instituto de Geofisica, Sede Michoacan, Universidad Nacional Autonoma de Mexico ; Université du Québec Dirección General y Dirección de Tecnología, Consorcio Minero Benito Juárez ; Université du Québec Éditeur(s) : HAL CCSD Springer/Terra Scientific Publishing Company Résumé : International audience We report oil the discovery of magnetite nanoparticles ranging in size from 2 to 14 full in the mineralized zones of the Pena Colorada iron-ore deposit, southern Mexico. Micrometric scale magnetite was magnetically reduced and divided into distinct size ranges: 85-56 mu m, 56-30 mu m, 30-22 mu m, 22-15 mu m, 15-10 mu m, 10-7 mu m and 7-2 mu m. Nanometric-scale magnetite in the size range 2-14 nm was identified. The magnetite was characterized by X-ray diffraction, transmitted and reflected light microscope, high-resolution transmission electron microscopy (TEM), high angle annular dark field, Mossbauer spectroscopy and its magnetic properties. Crystallographic identification of nanostructures Was performed using high-resolution TEM. Characteristic changes were observed when the particles make the size transition from micro- to nanometric sizes, as follows: (1) frequency-dependent magnetic Susceptibility percentage (chi FD%) measurements Show high Values (13%) for the 2-14 nm fractions attributed to dominant fractions of superparamagnetic particles; (2) variations of chi FD% < 4.5% in fractions of 56-0.2 mu m occur in association with the presence of microparticles formed by magnetite aggregates of nanoparticles (< 15 nm) embedded in berthierine; (3) Mossbauer spectroscopy results identified a superparamagnetic fraction; (4) nanometric and 0.2-3 mu m grain size magnetite particles require a magnetic field up to 152 mT to reach saturation during the isothermal remanent magnetization experiment; (5) coercivity and remanent magnetization of the magnetite increase when the particle size decreases, probably due to parallel Coupling effects; (6) two-magnetic Susceptibility versus temperature experiments of the same 2-14 nm sample show that the reversibility during the second heating is due to the formation of new magnetite nanoparticles and growth of those already present. during the first heating process. ISSN: 1343-8832 hal-00413053 https://hal.archives-ouvertes.fr/hal-00413053 | Partager
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