Óxidos de ferro magnéticos de um tufito da região do Alto Paranaíba, MG

The Mossbauer analysis along with the structural Rietveld refinement based on powder X-ray data for the magnetic fraction (saturation magnetization, s = 19 J T-1 kg-1) separated from a tuffite material from Alto Paranaiba, state of Minas Gerais, Brazil, reveal that a (Ti, Mg)-rich maghemite (deduced s = 17 J T-1 kg-1) and, for the first time observed in this lithodomain, magnesioferrite (characteristic s = 21 J T-1 kg-1) respond for the magnetization of the rock material. Consistent models for the ionic distribution in these iron-rich spinel structures are proposed.