Phys. Rev. Lett. 94, 108002 (2005)

Structure Formation in Electromagnetically Driven Granular Media

A. Snezhko, I. S. Aranson, and W.-K. Kwok

Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA

(Received 20 October 2004; published 18 March 2005)

We report structure formation in submonolayers of magnetic microparticles subjected to periodic electrostatic and magnetic excitations. Depending on the excitation parameters, we observe the formation of a rich variety of structures: clusters, rings, chains, and networks. The dynamics and shapes of the structures are strongly dependent on the amplitude and frequency of the external magnetic field. We find that for pure ac magnetic driving the low-frequency magnetic excitation favors compact clusters, whereas high frequency driving favors chains and netlike structures. An abrupt phase transition from chains to a network phase was observed for a high density of particles. ?2005 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v94/e108002


PACS: 45.70.Mg

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