Undulation instability in stripe domain structures of « bubble » material

Abstract

Two-dimensional smectic-like patterns form spontaneously in garnet plates of bubble material. We use the smectic analogy to explain the origin of the topological hysteresis of these stripe domain structures recently observed under magnetic field cycles. We show that these systems undergo an undulation instability as the magnetic field peak increases. We describe successively (1) the undulation instability similar to that of smectics A, (2) its transformation into a chevron structure and (3) the formation of fingers resulting in a complex labyrinth structure. Quantitative comparison is made with existing experiments