Synthesis and characterization of nanometric magnetite coated by oleic acid and the surfactant CTAB

For the intermediate and largest particles a mixture of magnetite and maghemite phases were produced as the saturation magnetization values of MS ∼ 60 emu/g indicated; these values were measured for most samples, independently of the coating surfactant concentration, and according to the ZFC-FC curves the blocking temperatures were 225K and 275K for the smallest and largest magnetite nanoparticles, respectively. The synthesis method was highly reproducible.Nanometric magnetite (nm-Fe3O4) particles were prepared by the reverse co-precipitation synthesis method, obtaining particle sizes that ranged from 4 to 8.5 nm. In their synthesis, the concentration of iron salts of ferric nitrate, Fe(NO3)3⋅9H2O, and ferrous sulfate, FeSO4⋅7H2O, were varied relative to the chemical reaction volume and by using different surfactants such as oleic acid (OA) and hexadecyltrimethylammonium bromide (CTAB). The nm-Fe3O4 particles were characterized by transmission electron microscopy (TEM), Mössbauer spectroscopy (MS), magnetic and X-ray diffraction (XRD) measurements

Meninas na F´Ä±sica: um desafio para a educa¸c˜ao cient´Ä±fica escolar∗

An overview of the activities of the Commission for Relations and Gender, an organization sponsored by the Brazilian Physical Society, is presented. The focus is on the mainframe of basics action, where the popularization and education in sciences directed to girls in high school is a central activityUma avalia¸c˜ao das atividades da Comiss˜ao de Rela¸c˜oes de Gˆenero da Sociedade Brasileira de F´ísica ´e apresentada. A ˆenfase est´a nos eixos de a¸c˜oes b´asicas, onde se destaca as atividades de divulga¸c˜ao cient´Ä±fica em f´Ä±sica voltadas para as meninas nas escolas

Quantum critical behavior in a CePt ferromagnetic Kondo lattice

6 p. : il.Most of the studies of heavy fermions near a quantum critical point QCP have been carried out on antiferromagnetic systems. In this paper we report on the disappearance of ferromagnetic FM order in CePt as seen by the ac magnetic susceptibility and the electrical resistance measurements under pressures P up to 15 GPa. The pressure dependence of the Curie temperature TC P follows a typical Doniach’s phase diagram for Kondo lattice systems and it is consistent with a QCP at the critical pressure PC 12.1 GPa. The resistance in the vicinity of the QCP shows clearly a non-Fermi liquid NFL and beyond that a Fermi liquid FL state is recovered. A semiquantitative discussion on the nature of the vanishing of TC in a FM Ce Kondo lattice is given for the first time