Statistical mechanics of magnetic bubble arrays. I. Topology and thermalization

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Abstract
Bubble domains in thin magnetic garnet films are an experimentally accessible two-dimensional system with well-characterized properties. Bubble arrays can be directly viewed with polarized light using optical microscopy, digital imaging, and computer-video techniques. The structure and dynamics of topological defects can be studied in detail. We present observations of the interactions and dynamics of defects in magnetic bubble arrays. Quasithermal Brownian motion of bubbles in an applied ac magnetic field arises from microscopic substrate roughness. Experimental measurements of diffusive bubble motion are used to estimate the effective temperature, and the effective pinning energy and length scales for microscopic roughness in the garnet film.