Evolution of disorder in magnetic stripe domains. II. Hairpins and labyrinth patterns versus branches and comb patterns formed by growing minority component.

Abstract

An analysis is presented of the role of topological defects in the evolution of disordered stripe-domain phases of ferrimagnetic garnet films. Proliferation by continued nucleation and topologically constrained unbinding of disclination dipoles are identified as the essential mechanisms mediating the strain-induced disordering process. Two distinct classes of metastable, disordered states are distinguished on the basis of the relative predominance of defect-pair proliferation and unbinding, and the fundamentally different corresponding pattern morphologies which accommodate the emerging disclination network. Striking patterns containing linear chains of interdigitated disclination dipoles are representative of the first class, while labyrinthine patterns, exhibiting a robust and well-defined local structure in the form of ``cybotactic'' clusters, are typical of the second class. Results are discussed with reference to defect-mediated melting and the structure of glasses. Comparison is also made with pertinent phenomena in related systems such as ferrofluids and amphiphilic films.