Fabrication of artificial crystals with tunable lattice constant via self-assembly of floating magnetic particles

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 containers with Roaring magnets. Computer simulations of electromagnetic wave propagation in such three-dimensional structures suggest an opening o f a tunable photonic bandgap in the microwave range. (C) 2001 Elsevier Scie nce B.V. All rights reserved.