INFLUENCE OF APPLIED MAGNETIC FIELD UPON THE COMPLEX PERMEABILITY IN AN MnZn FERRITE AND ITS COMPOSITES

Rastislav Dosoudil - Vladimír Olah - Vladimír Ďurman

   The article deals with the influence of a dc magnetic field upon the complex permeability spectra in an MnZn sintered ferrite and its composites in the frequency range from 10kHz to 1.6GHz under magnetic fields up to 100kA/m. In the case of the sintered ferrite, the spectrum of m' has a resonance type frequency dispersion above 150kHz which can be caused mainly by the domain walls vibrations and the spectrum of m'' has a maximum at about 750kHz (at H_dc=0kA/m). In the presence of a dc magnetic field, the dispersion character changes from resonance type to relaxation type spin resonance with disappearance of the domain walls. The values of m' in the frequency region above 1.5MHz are probably decreased because of eddy current effect. In the case of composites, the resonance type of frequency dispersion of permeability is observed above 150MHz and it can be attributed to the spin resonance, which is stabilized by the demagnetising field in the ferrite particles dispersed in the non-magnetic polymer matrix.

Keywords: MnZn sintered ferrite, composite material, dc magnetic field, complex permeability spectrum, resonance

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