Optical forces from an evanescent wave on a magnetodielectric small particle.

We report the first study on the optical force exerted by an evanescent wave on a small sphere with both electric and magnetic responses to the incident field, immersed in an arbitrary nondissipative medium. New expressions and effects from their gradient, radiation pressure, and curl components are obtained owing to the particle induced electric and magnetic dipoles, as well as to their mutual interaction. We predict possible dramatic changes in the force depending on the host medium, the polarization, and the nature of the surface wave.