COARSENING OF CELLULAR DOMAIN PATTERNS IN MAGNETIC GARNET-FILMS

We experimentally study the coarsening of two-dimensional cellular domain patterns in an increasing bias field. As in soap froths and polycrystalline materials, the coarsening is driven by effective cell surface energy. We find that the domain patterns are distinguished by a nonmonotonic change in the total cell surface energy and by topological evolution that proceeds almost exclusively by cell elimination. Aboav's law describing topological correlations between neighboring cells is found to hold over a wide range of bias and cell density. We have also evaluated the distribution P(n) of n-sided cells over three decades in cell density. The patterns show a form of partial scaling: over a two-decade drop in cell density, the fraction of all cells that are pentagonal bubble traps (fivefold symmetric domain structures containing trapped magnetic bubbles) remains nearly constant at f50.2 while P(n) changes rapidly. The partial scaling may be related to a novel topological structure in which the bubble traps act as stable fivefold vertices. © 1990 The American Physical Society.