Surface/interface-roughness-induced demagnetizing effect in thin magnetic films

Abstract

We study the influence of surface/interface roughness on the demagnetizing factor of a thin magnetic film with a single or a double boundary of self-affine, mound or anisotropic roughness. For a film with a single self-affine rough boundary, the in-plane demagnetizing factor ${N}_{\mathrm{xx}(\mathrm{yy})}$ is proportional to the interface width w square and to the leading order is inversely proportional to the lateral correlation length \ensuremath{\xi}. The roughness exponent \ensuremath{\alpha} is also shown to greatly affect ${N}_{\mathrm{xx}(\mathrm{yy})}.$ For a film with a single mound boundary, ${N}_{\mathrm{xx}(\mathrm{yy})}$ is inversely proportional to the apparent correlation length, and also depends on the ratio of the two different lateral lengths: the average mound separation \ensuremath{\lambda} and the randomness correlation length \ensuremath{\zeta}. It is also shown that an anisotropic surface morphology can induce anisotropic in-plane demagnetizing factors. The demagnetizing anisotropy can be magnified by a morphological anisotropy. Furthermore, we consider films with two rough boundaries. Besides a general formalism derived for the demagnetizing factor, we investigate how the cross correlation of the two rough boundaries affects the in-plane demagnetizing factors. Connections between the demagnetizing factor and thin-film growth mechanisms are also discussed.