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 Hdc=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