Frequency dispersion of complex permeability of Y-type hexagonal ferrites

The frequency characteristics of Y-type hexagonal ferrites were studied. The samples were prepared by the conventional ceramics method. X-ray diffraction was used to characterize the phase formation. The microstructure was observed via scanning electron microscopy, and magnetic properties were investigated using vibrating samples magnetometer and impedance analyzer. Experimental results show that composition and processing will determine the magnetization mechanism of Y-type hexagonal ferrites in very high frequency and ultra high frequency. Both domain wall motion and magnetization rotation exist in magnetization processing. There is a double resonance peak with obvious dispersion character for low Co substitution. Co substitution will increase the magnetic anisotropy distinctly. As Co content rises, the increasing magnetic anisotropy leads to the movement of resonance peak towards higher frequency and disappearance of magnetic domain wall resonance; initial permeability decreases at the same time. The rise of sintering temperature will enhance magnetic domain wall resonance remarkably and move resonance peak towards lower frequency. (C) 2003 Elsevier B.V. All rights reserved.