Magnetic properties of MnFe2O4 nano-aggregates dispersed in paraffin wax

Manganese ferrite, MnFe2O4 nanoparticles with average size of similar to 6.5 nm were synthesized by using a thermal decomposition method. The nanoparticles were aggregated which was confirmed by FESEM and TEM images. The aggregates with a diameter of similar to 50 rim showed interacting superspin glass (SSG) behavior The powders were dispersed in the molten paraffin wax by using ultrasonic bath. Samples with different paraffin/ferrite weight ratios of P/F = 0, 1, 5, 10 and 20 were prepared. M-H curves of the samples revealed presence of superparamagnetic state at 300 K. Saturation magnetization (M-s) decreased from 26.6 to 1.3 emufg by increasing the P/F value from 0 to 20, respectively. Furthermore, the VSM measurements showed a decrease in surface spin disorder of paraffin-embedded nanoparticles in comparison with bare particles. The AC magnetic susceptibility peak temperature, T-p increased from 230 to > 300 K with increasing the paraffin content in the samples. The present study showed that by dispersing the particles in a non-magnetic matrix, the blocking temperature could be increased. (C) 2015 Elsevier B.V. All rights reserved