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

Abstract

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 11, 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 14 emu/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.