Surface Magnetic Canting in a Ferromagnet

The surface magnetic canting (SMC) of a semi-infinite film with ferromagnetic exchange interaction and competing bulk and surface anisotropies is investigated via a nonlinear mapping formulation of mean-field theory previously developed by our group [L. Trallori, M. G. Pini, A. Rettori, M. Maccio`, and P. Politi, Int. J. Mod. Phys. B 10, 1935 (1996)], and extended to the case where an external magnetic field is applied to the system. When the field Hpar is parallel to the film plane, the condition for SMC is found to be the same as that recently reported by Popov and Pappas [Phys. Rev. B 64, 184401 (2001)]. The case of a field Hperp applied perpendicularly to the film plane is also investigated. In both cases, the zero-temperature equilibrium configuration is easily determined by our theoretical approach.