Síntese e caracterização estrutural e magnética dos sistemas LaMTO3(MT = Cr, Fe e Mn)

Abstract

In this work were obtained nanoparticles of LaMTO3 (MT – Cr, Fe and Mn) with particles sizes between 20 to 100 nm using the co-precipitation method. Systems containing different concentrations of sucrose were prepared to study the influence of the chelating agent in the growth of nanoparticles. All samples were analyzed using structural and magnetic techniques of characterization. X-ray diffraction (XRD) results added to the Rietveld refinement analysis of the X-ray powder diffraction data confirmed the formation of the main phases in all the systems prepared, with and without addition of sucrose. All prepared systems we have observed the dependence of the size with the synthesis temperature. The system LaCrO3 and LaFeO3 showed a decrease in particle size to the samples prepared with addition of sucrose. However to the set of samples of the LaMnO3 we have not observed significant changes in particle size by the addition of sucrose when compared to samples without the addition of the same. Overall it was observed that the concentration of 0,02mol/L sucrose was the best condition with control of the sizes of nanoparticles. The results of magnetization measurements as a function of magnetic field and temperature show that the systems studied are antiferromagnetic. Furthermore, these results show that systems of LaMTO3 (Cr, Fe and Mn) exhibit a strong dependence of Neél temperature (TN) with the particle size.