Magnetic entropy change in zinc-ferrite nanoparticles synthesized by using a sonochemical method

In order to investigate the magnetic entropy change in magnetic nanoparticles, we synthesized zinc-ferrite nanoparticles by using a sonochemical method. All peaks of the X-ray diffraction patterns could be attributed to a cubic spinel structure with a lattice constant a(0) = 8.45 angstrom. The average size of the particles estimated by using the Scherrer formula was 13.4 nm. The Curie temperature Tc, determined from the temperature of the maximum value in vertical bar dM/dT vertical bar, was found to be about 140 K. The maximum value of -Delta S-M in a field of 20 kOe was found to be about 0.20 J/kg center dot K. The maximum value of -Delta S-M increased as the applied field was increased.