Abstract
Two-dimensional magnetic films with perpendicular magnetization spontaneously form magnetic domain patterns that evolve or undergo symmetry transformations as a function of temperature. When the system is driven from equilibrium by a rapid change in temperature, topological pattern defects are the elementary pattern excitations that affect this evolution. An elastic continuum model is adapted to describe how a metastable population of topological defects alters the domain density and the magnetic susceptibility of the "stripe" magnetic domain pattern. Temporal changes in the susceptibility are interpreted using a dynamical equation describing the defect population. Recent experiments provide a quantitative verification of the model, and illustrate the use of the magnetic susceptibility to follow the population dynamics of topological defects in this system, and its potential role in investigating a pattern melting phase transition.