Magnetic properties of low Mn-doped NiCuZn nanocrystalline ferrites

Low Mn-doped NiCuZn ferrites with compositions of(Ni0.6Zn0.3Cu0.1)(1-x)MnxFe2O4 (where x=0,0.01, 0.02 and 0.03) were synthesized directly with sol-gel method. The influence of the Mn2+ content (parameter x) and the sintered temperature on the microstructure and the magnetic properties of these ferrites were mainly discussed. With the increasing Mn2+ content, saturation magnetization (M-s) of the powder samples decreased. Saturation magnetic flux density (B-s) and remnant magnetic flux density (B-r) of the toroidal specimens decreased with the Mn2+ content up to x = 0.02, followed by increasing. B-r and B-s both increased with the increasing sintered temperature, while coercivity (H-c) decreased. The real part of permeability (mu') of the toroidal specimens increased up to x = 0.01, followed by decreasing. The sintered temperature also affected the resonance frequency and the useable frequency (from which the value of tan 3 increased more) obviously. Furthermore, the low-frequency permeability and the secondary maximum (the maximum of the permeability appearing the secondary time) both increased with the sintered temperature from 70 to 120 and 150 to about 600. (C) 2008 Elsevier B.V. All rights reserved.