The effect of agarose agent on the structural, magnetic and optical properties of barium hexaferrite nano-particles synthesized by sol-gel auto-combustion method

The main goal of this study is to improve the structural, magnetic and optical properties of the M-type barium hexaferrite nano-particles by addition of agarose as a natural agent, which were synthesized by the sol-gel auto-combustion method. For this purpose, properties of the synthesized samples were characterized by DTA-TGA, XRD, FT-IR, FE-SEM, TEM, VSM, and UV-Vis-DRS analyses. The DTA-TGA thermal analyses showed that agarose as a fuel agent could reduce the starting temperature of crystallization in the precursors. Also, based on these results, the temperature of 800 degrees C was chosen as the calcination temperature of the precursors. XRD patterns confirmed the formation of pure M-type barium hexaferrite without any impurities after calcination at 800 degrees C. The presence of agarose caused a more homogeneous distribution of metal cations Fe3+ and Ba2+ and the precursor was more easily and completely transformed into hexagonal barium ferrite in the presence of this agent. Also, the Rietveld refinement reported a decrease in average crystallite size from 49.4 to 29.6 nm by adding agarose. In addition, FE-SEM and TEM images showed that the agarose agent significantly reduces the average particle size and also prevents agglomeration of particles. Moreover, magnetic studies indicated that the presence of agarose led to the simultaneous increase of coercivity and remanence magnetization, resulting in an increase of maximum energy product from 0.81 to 0.92 MGOe. Also, the band gap energy (Eg) of the synthesized samples was found in the range of 2.36-2.76 eV. Finally, the significant effect of the agarose agent on the properties of BaFe12O19 nano-particles was clearly explained.