Gyroresonance in unsaturated composite bodies: Experiments and theory

The permeability spectra of composite magnetic materials (NiZn ferrite comp osites and YIG composites) has been experimentally studied on a wide range in magnetic load C. The resonance frequency decreases with the increasing m agnetic load of the mixture. This is attributed to the fading of the magnet ic pole on the surface of the magnetic inclusions. A theory is developed wh ich is intended to give an expression for the gyroresonance frequency of ma gnetic composites in their unsaturated magnetic state. It fits the experime ntal data over its full range of volume fraction C without any corrective f actors. The proposed relation, which is an extension of the Kittel's expres sion for the resonance frequency of a saturated body, points out a notewort hy close link between the concept of reciprocity and the one of demagnetiza tion. (C) 2000 American Institute of Physics. [S0021-8979(00)53508-7].