FERROMAGNETIC-RESONANCE IN A SUSPENSION OF SINGLE-DOMAIN PARTICLES

The theory of ferromagnetic resonance (FMR) in an assembly of single-d omain uniaxially anisotropic particles is being applied to suspensions . The approach used has, as its basis, the independent-grain model onc e proposed for the description of FMR in polycrystals. We surmise that the basic assumptions of this model are also appropriate for composit es of fine magnetic particles. With regard to the specific properties of the systems in question, we extend the model taking into account (i ) the thermofluctuational effects (superparamagnetism) and (ii) the or ientational mobility of the particles which leads to the change of the orientational distribution of their anisotropy axes under the influen ce of the applied field. The joint action of these effects imparts som e specific features to the FMR spectra of a magnetic suspension. For e xample, in a certain temperature range two peak absorption lines must occur.