Síntese e caracterização de Perovskitas duplas com Estequiometria La2CrBO6 com B = Fe, Co e Ni - determinação de suas propriedades magnéticas

Abstract

Metal oxides have several interesting physical properties ranging from, for example, ferroelectricity, colossal magnetoresistance, to superconductivity, thus occupying a prominent position in the modern technological scene. The perovskite structure is the basis of a large number of oxides containing transition metals that exhibit these varied physical properties. In this work we report the synthesis and characterization of perovskites with stoichiometry LaCrBO6 (B = Fe, Co and Ni) highlighting the effect of transition metals on magnetic properties. The perovskites were synthesized by an alternative route to the traditional sol-gel, using the gelatin as a chelating agent and calcined at 1200 ºC / 2h and 1000ºC / 2h. The X-ray diffraction (XRD), using the Rietveld method, scanning electron microscopy (SEM) with the aid of energy dispersive analysis (EDS) and its magnetic characteristics were obtained by means of of Mossbauer spectroscopy and magnetization measurements. The perovskite structure was investigated by the combination of the X-ray diffraction results, allied to the refinement and showed mainly the formation of perovskite phase and secondary phases in all the samples. Hysteresis curves and magnetic measurements at low temperatures showed a ferromagnetic behavior for all samples. At room temperature a paramagnetic behavior was observed for the samples with iron and nickel and an antiferromagnetism declined (canted) for the sample with cobalt. It is also possible to verify a technologically important phenomenon known as "exchange bias" in the samples with iron and cobalt.