High temperature magnetic properties of Co1-xMgxFe2O4 nanoparticles prepared by forced hydrolysis method

In this work, we study the effect of Mg2+ nonmagnetic ions on the magnetic properties of cubic Co1-xMgxFe2O4 mixed nanostructured ferrites synthesized by a forced hydrolysis method. Magnetization measurements show that all specimens are superparamagnetic at room temperature, and the saturation magnetization (M-s) decreases with increasing the molar magnesium concentration, being 260 emu/cm(3) and 160 emu/cm(3) for x = 0.0 and 0.6, respectively. The Curie temperature T-C, similar to 740 K is determined by means of the inverse of the susceptibility versus temperature and slightly depends on the Mg content. The effective anisotropy constant, (K-eff) decreases with substitution of Co2+ ion by nonmagnetic Mg2+ ions in the spinel structure. These results are discussed in terms of interparticle interactions induced by the thermal fluctuations, cation distribution and other imperfections that could increase with temperature. (C) 2012 American Institute of Physics. [doi:10.1063/1.3677923]