Theory of Faraday rotation in granular magnetic materials

We present a formalism to treat Faraday rotation (FR) in composite media. The method is not limited to low concentrations of magnetically active inhomogeneities and is thus useful for understanding the magneto-optical properties of such inhomogeneous media over the whole range of concentrations. It involves the calculation of an effective magnetic-field-dependent dielectric tensor εe using a tensor effective-medium approximation. To illustrate the technique, we present the results of several model calculations involving both paramagnetic and ferromagnetic metals. We find that such materials have strongly enhanced FR over a wide range of frequencies. The effects of particle shapes on FR are discussed.