Magnetic properties of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn ferrites synthesized by reverse micelle technique

Nanocrystalline nickel-zinc, zinc-manganese, and nickel manganese ferrites synthesized by reverse micelle synthesis technique were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction, and the magnetic behavior studied by Superconducting Quantum Interference Device. The mixed (Ni-Zn, Zn-Mn, and Ni-Mn) ferrites exhibit blocking temperatures of H, 20, and 15 K, respectively. The small differences in the blocking temperatures are attributed to the magnetocrystalline anisotropy and L-S coupling. The saturation magnetization of nanocrystalline Ni-Zn, Zn-Mn, and Ni-Mn at 300 K was 4.5, 9, and 7 emu/g, respectively, and at 2 K was 15, 19, and 14emu/g, respectively. The lower saturation magnetization of the nanocrystalline ferrites compared to their bulk counterparts is attributed to the core-shell morphology of the particles consisting of ferromagnetically aligned core spins and a spin-glass-like surface layer. (C) 2004 Elsevier B.V. All rights reserved.