A combiation of video polarization microscopy and extensive digital line pattern analysis has been invoked to examine in quantitative detail the transformation of a lamellar into a ‘‘labyrinthine’’ magnetic-stripe domain pattern. The evolution of disorder is found to be mediated by a sequence of transverse, ‘‘smectic’’ instabilities culminating in the generation of disclination dipoles. Their subsequent continuous ‘‘unbinding’’ facilitates the formation of a globally isotropic nonequilibrium pattern adopting the topology of a binary tree and displaying a well-defined morphology with a motif in the form of oblong, polygonal clusters of linear-stripe segments.

• Received 22 August 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.2460