Magneto-transport and magneto-optics in composite media with a two-dimensional microstructure

In the presence of a strong in-plane magnetic field B, the electrical transport and optical properties of thin composite films with a columnar microstructure exhibit surprising new forms of behavior. These are caused by the appearance of local currents which flow up and down in the perpendicular direction, and increase as |B| without any saturation. In a conducting composite, this results in a positive, non-saturating magneto-resistance, that is proportional to B². When the microstructure is periodic, the magneto-resistance exhibits a strong dependence on the precise directions of B and of the average in-plane current 〈J〉 with respect to that microstructure. The optical properties of metal/dielectric composite films with a periodic columnar microstructure can also exhibit such strong directional variability, if the microstructure and B and the frequency are adjusted so that the system is in the vicinity of a sharp quasi-static resonance. In a metallic film with a periodic array of small, sub-wavelength holes, it is possible to achieve a strong, anisotropic transmissivity by adjusting the system parameters so as to operate near a B-dependent `surface plasmon resonance'.