Magnetic study of nanoparticles of Mg_0.95Mn_0.05Fe₂O₄ spinel ferrite

Abstract

Magnetization of nanoparticles of Mg-Mn ferrite, synthesized using high energy ball milling has been studied. X-ray diffraction pattern of the particles milled for 6 h confirmed the single-phase cubic spinel structure with a lattice parameter of 8.47 Å. Langevin function fitting on M-H data at 300K gives a log-normal particle size distribution with median diameter of 6.4 nm and standard deviation 0.7. The isothermal <i style="">dc</i> magnetization studies have been performed using SQUID and vibrating sample magnetometer in the temperature range 5-300 K. These measurements show that the sample is superparamagnetic above the blocking temperature <i style="">T</i>_B ~ 246 K. The reduction in saturation magnetization in the case of nanoparticles has been explained on the basis that the magnetic moments in the surface layers outside the core are in a state of frozen disorder.