Self-assembly of floating magnetic particles into ordered structures: A promising route for the fabrication of tunable photonic band gap materials

We report stable ordered arrays of millimeter-size magnetic particles float ing on a liquid surface. Self-assembly into a regular two-dimensional latti ce results from lateral magnetic interactions between the particles. The la ttice constant may be easily tuned by the application of external magnetic field. The array symmetry is designed by using different particle shapes, m agnets, and magnet position inside the particle, so that complex symmetries may be achieved. Three-dimensional ordered arrays are obtained in a stack of troughs containing floating magnets. Computer simulations of electromagn etic wave propagation in such three-dimensional structures suggest an openi ng of a tunable photonic band gap in the microwave range. (C) 1999 American Institute of Physics. [S0003-6951(99)01352-2].