  The mutual electromagnetic correlations between two spatially separated
systems gives rise to Casimir and Casimir-Polder effect. The corresponding
forces, which are generally attractive for most vacuum-separated metallic or
dielectric geometries, are due to the contribution to the ground-state energy
of the coupled system. We investigate here the Casimir-Polder free energy
corresponding to interactions of a magnetically and electrically polarizable
micro-particle with a magneto-dielectric sheet. Our semi-phenomenological study
shows that such an interaction is reversibly tunable in strength and sign.The
latter, particularly, is true provided we look for the exotic materials
fabricated at scales between the micron and the nanometer. The crossover
between attractive and repulsive behavior is found to depend on the
polarizability ratio of the micro-particle and the electromagnetic impedance of
the magneto-dielectric sheet.
