Abstract
We investigate the morphological instability of ferromagnetic planar thin films using linear perturbation theory. We find that, for a uniformly magnetized ferromagnetic planar film with a nonzero component of the magnetization along the normal to the planar film, the planar surface is unstable with respect to perturbations having a wave number smaller than a critical value. In addition, the critical wave number changes with the direction of the surface perturbations, with the perturbations perpendicular to the in-plane component of the magnetization having the largest critical wave number. Such anisotropy could be important in controlling the evolution of the morphology of the film and nanoscale-island formation. © 2009 American Institute of Physics.