A self-consistent effective-medium approximation is applied to the problem of ferromagnetic inclusions in the composite medium to determine the effective magnetic susceptibility. As the derivation utilizes the tensor form of ferromagnetic susceptibility, the obtained equations are valid in the vicinity of the ferromagnetic resonance, where the susceptibility of a ferromagnetic inclusion has significant off-diagonal components. In addition, the static magnetization of neighboring inclusions is taken into account through an effective magnetization of the effective medium. Three most interesting cases are examined, namely, a fully magnetized composite, a composite with single-domain particles, and a composite with demagnetized particles. The effective susceptibility of a magnetized composite is most interesting since the effective susceptibility has the tensor form, significantly varies with changing of the volume fraction of inclusions, which includes shifting of the resonance frequency, and differs from the noninteracting case even at very low volume fractions. In contrast, the effective susceptibility of a composite with isotropically oriented single-domain particles is scalar, without notable shift of resonance frequency, and varies only moderately with changing of the volume fraction. The case of composite with demagnetized inclusions is discussed only qualitatively since the derivation of effective susceptibility greatly depends on the particular physical state of the inclusions.

• Received 14 July 2004

DOI:https://doi.org/10.1103/PhysRevB.71.174418