Surface anisotropy in ferromagnetic prolate spheroids

The eigenvalue for nucleation by the curling mode, in the presence of surfa ce anisotropy, is approximated by a rational function of both the radius an d the aspect ratio of a general prolate spheroid. This approximation makes it easy to take the surface anisotropy into account without getting into cu mbersome and complicated computations, and should facilitate the check of c omputational micromagnetics results against the analytic constraints. The a pproximation is rather crude, but it should be useful for cases in which th e computations need to be repeated many time, as is the case of finding the best fit of the anisotropy constant to a set of experimental data. (C) 200 0 American Institute of Physics. [S0021-8979(00)15708-1].