Navegando por Autor "Câmara, M. S. A."
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Artigo Magnetic behavior of nanocrystalline MnCo2O4 spinels(Elsevier, 2006-07) Araújo, José Humberto de; Borges, Filipe Martel de Magalhães; Melo, Dulce Maria de Araújo; Câmara, M. S. A.; Martinelli, Antonio Eduardo; Soares, João Maria; Cabral, F. A. O.A series of powders with different particle sizes of the spinel MnCo2O4 was synthesized by the Pechini method. The resulting precursor was calcined between 400 and 900o and characterized by thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetization measurements. TGA analysis showed a loss of mass in the region from 200 to 650oC and stability after this. XRD patterns showed an increase of the crystallite size with calcination temperature. Magnetization measurements on the sample calcined at 900oC showed an unusual behavior of the hysteresis curve and irreversibility of the magnetization with field cooled (FC) and zero field cooled (ZFC) procedures. An evolution of this behavior was observed with increasing crystallite size