Pattern formation in a monolayer of magnetic spheres.
Pattern formation is investigated for a vertically vibrated monolayer of magnetic spheres. The spheres of diameter D encase cylindrical magnetic cores of length l. For large D/l, we find that the particles form a hexagonal-close-packed pattern in which the particles' dipole vectors assume a macroscopic circulating vortical pattern. For smaller D/l, the particles form concentric rings. The static configurational magnetic energy (which depends on D/l) appears to be a determining factor in pattern selection even though the experimental system is driven and dissipative.
Stambaugh
Justin
J
Institute for Research in Electronics and Applied Physics, Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
Lathrop
Daniel P
DP
Ott
Edward
E
Losert
Wolfgang
W