A comparison of the magnetic characteristics of nanocrystalline nickel, zinc, and manganese ferrites synthesized by reverse micelle technique

Nanocrystalline nickel, zinc and manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction techniques, and the magnetic behavior studied by Superconducting Quantum Interference Device (SQUID). The three ferrites exhibit blocking temperatures of 16, 20, and 35 K, respectively. The difference in the blocking temperatures was attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of the three ferrites at 300 K was 25, 8, and 6 emu/g, respectively and at 2 K was 35, 17, and 15 K, respectively. The lower saturation magnetization in the case of nickel and manganese ferrite compared to their bulk counterparts is attributed to a core-shell like particle morphology. The increase in the saturation magnetization in the case of zinc ferrite nanoparticles is attributed to the change in the cation distribution from a normal spinel to a mixed spinel structure in the nanocrystalline form. (C) 2004 Elsevier B.V. All rights reserved.