High temperature magnetic properties of magnesium ferrite nanoparticles

Magnetic properties such as Curie temperature (T-C), saturation magnetization (M-s), remanent magnetization (M-r), and coercivity (H-c) of nanoparticles of magnesium ferrites (MgFe2O4) were studied in a broad range of temperatures varying from room temperature to 800 K. The magnetization decreases with increasing temperature, approaching 0 at similar to 750 K. The Curie temperature, determined by means of the inverse susceptibility versus temperature, was similar to 738 K. The saturation magnetization, coercivity, and remanence decreased with increasing temperature, being close to 0 at temperatures near T-C. However, for temperatures 100 K above room temperature, these magnetic properties were still the same as those at room temperature. The coercivity temperature dependence could be expressed in terms of T-3/4, indicating that MgFe2O4 nanoparticles may form a system of random and noninteracting identical particles. The results are discussed in terms of interparticle interactions induced by the thermal fluctuations, cation distribution, and other imperfections that exert fields on Mg2+ ions that could increase with temperature. (C) 2011 American Institute of Physics. [doi:10.1063/1.3536790]