Domain nucleation stability

Micromagnetic nucleation theory determines the conditions under which an infinitesimal nonuniform deviation from uniform magnetic saturation (nucleation mode) becomes energetically favorable. A method is described for deciding whether such a nucleation mode remains small or has a tendency to grow spontaneously, i.e., whether nucleation is stable or unstable. Approximations are developed that permit a simple application of the theory to uniaxial films with the anisotropy type used in bubble-domain devices. With these approximations calculations can be carried out analytically, and explicit expressions are obtained for the nucleation stability range. The expected behavior of the incipient domain pattern is interpreted with the help of a free-energy surface whose topography reflects the micromagnetic nucleation theory.