A method for determining the magnetic anisotropy profile of an ion‐implanted garnet layer is presented. To do this the eigenvalue equation for spin waves is solved numerically for a system consisting of a very thick film with uniform perpendicular anisotropy and a surface layer in which the anisotropy varies through the surface. Results of this calculation are matched to experimental FMR data from samples cut from the same wafer but etched by different amounts. A measurement of the exchange constant in the implanted layer may be possible if two or more surface modes are visible. The anisotropy profiles of samples implanted with 2×1014Ne+/cm2at 50, 100, and 150 keV were reconstructed in this manner. The profile was found to show a broad peak centered at a depth somewhat shallower than the projection range for Ne+at the appropriate energy. The value of the change in anisotropy was shown to match that predicted from a magnetostrictive origin and the measured change in lattice constant in the surface layer. The measured exchange constants in the implanted layer were 1.1×10−7and 1.7×10−7ergs/cm for 100‐ and 150‐keV implanted samples, respectively.