Magnetic Entropy Change in Zinc-Ferrite Nanoparticles Synthesized by Using a Sonochemical Method

Magnetic Entropy Change in Zinc-Ferrite Nanoparticles Synthesized by Using a Sonochemical Method Jun Hee Cho, Sang Gil Ko and Yangkyu Ahn Department of Chemistry, Konyang University, Nonsan 320-711 Eun Jung Choi Department of Opthalmic Optics, Konyang University, Daejeon 302-718 (Received 14 May 2008) 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 di raction patterns could be attributed to a cubic spinel structure with a lattice constant a0 = 8.45 A. 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 j dM=dT j, was found to be about 140 K. The maximum value of SM in a eld of 20 kOe was found to be about 0.20 J/kg K. The maximum value of SM increased as the applied eld was increased. PACS numbers: 75.30.Sg, 75.60.Ej, 75.75.+a