Structure and magnetic properties of Mn(Zn)Fe2−xRExO4 ferrite nano-powders synthesized by co-precipitation and refluxing method

Abstract

The spinel-type MnZn ferrite nanopowders were synthesized by co-precipitation and refluxing method using δ-FeOOH as a precursor. The effects of processing parameters such as the pH value of co-precipitation solution and reflux time on the crystalline phase formation, microstructure and magnetic properties were systematically investigated. The results showed that, instead of spherical shape, Mn0.5Zn0.5Fe2O4 nanoparticles have square slice shape with sizes varying from < 10 nm to > 20 nm. The particle size can be controlled by the co-precipitation and reflux parameters. The products with saturation magnetization (Ms) of 46 emu/g were obtained when the pH value of co-precipitation solution and reflux time are 13.0 and 6 h, respectively. The effects of rare earth (RE) elements (La, Nd, Gd) doping on the structure and magnetic properties of Mn0.4Zn0.6Fe$2−xRExO4 nanoparticles were investigated. Due to the differences in available magnetic moment and ion's radius for La3+, Nd3+ and Gd3+, various magnetic properties were obtained in these three series of alloys. It was also found that the particle size, Ms and the coercive force (Hc) strongly depend on the RE concentration due to the preferred occupied positions of RE ions.