The role of chelating agents on the structural and magnetic properties of α - Fe2O3 nanoparticles

Full text: In this work we have studied the influence of the insertion of chelating agents (AC) on the synthesis process of Fe2O3 nanocrystals obtained by co-precipitation method. X-ray diffraction (XRD) added to the magnetization results show that the addition influence significantly on the control particles size and the sizes distribution (presenting a average crystallite size around 6(2) nm). Therefore the nanoparticles prepared without organic precursor present average size of 75 nm and temperature dependent field cooling magnetization showed that there was Morin transition. Rietveld refinement analysis added to image of Scanning Electronic Microscopy show that for low concentrations of sucrose the particles shape are changed of randomly form to rod-like and directed to a preferential growth in 110 crystalline plane. Zero Field Cooling-Field Cooling (ZFC-FC) magnetizations curves show that samples obtained in low temperature present a superparamagnetic behavior with blocking and irreversibility temperatures around 95 and 135K, respectively. Besides, a more careful analysis performed in the XRD, SEM, TEM and ZFC-FC magnetization data show clearly the dependence of the size, shape and size distribution of the samples as function of the chelating agent concentration. We have concluded that the presence of sucrose in the synthesis inhibited the coalescence effect and provoke change in crystallite shape (CNPq). (author)