We report on investigations of single and multiple scattering of electromagnetic (EM) waves in the presence of magnetic scatterers and their implications to the localization parameter, to the energy transport velocity and to the diffusion constant. Single scattering of EM waves by magnetic particles presents some unusual features, such as forward-backward asymmetry and resonances, even in the small-particle limit. The total scattering cross-section and asymmetry factor depend on the magnetic permeability of the scatterers. In multiple scattering, this alters the localization parameter through the transport mean free path. In particular, we have shown that the presence of magnetic scatterers induces a global decrease in the localization parameter, which also exhibits an oscillatory dependence on the scatterer magnetic permeability [1]. By considering magnetic scatterers following the Curie-Weiss susceptibility law, we suggest that the localization parameter can be tuned by varying the temperature [1]. In addition, we have shown that the diffusion constant of wave propagation in the medium is strongly affected in the presence of magnetic scatterers, not only through the transport mean free path, but also through the transport velocity [2]. The fact that single EM scattering by magnetic particles exhibits a characteristic resonant behavior, even in the small-particle limit, introduces an extra time delay in wave propagation, causing a decrease in the transport velocity if compared with the nonmagnetic case [3]. This fact, as well as the global decrease in the transport mean free path induced by the presence of magnetic particles, leads to extremely small values of the diffusion constant.
[1] F. A. Pinheiro, A. S. Martinez, and L. C. Sampaio, "New Effects in Light Scattering in Disordered Media and Coherent Backscattering Cone: Systems of Magnetic Particles", Phys. Rev. Lett. 84, 1435 (2000).
[2] F. A. Pinheiro, A. S. Martinez, and L. C. Sampaio, "Vanishing of Energy Transport Velocity and Diffusion Constant of Electromagnetic Waves In Disordered Magnetic Media", submitted for publication.
[3] M. P. van Albada, B. A. van Tiggelen, A. Lagendijk, and A. Tip, "Speed of Propagation of Classical Waves in Strongly Scattering Media", Phys