Probing dynamical magnetization pinning in circular dots as a function of the external magnetic field orientation

We performed ferromagnetic resonance measurements of square arrays of noninteracting Permalloy circular dots for different orientations of external magnetic field with respect to the patterned film plane (theta). Out-of-plane angular dependence of the main resonance peak was measured in the whole range of the field angles 0 degrees <= theta <= 90 degrees. The main eigenmodespatial distribution is strongly nonuniform due to the dot nonellipsoidal shape. Nevertheless, for dots with small aspect ratio b = L/R <= 0.1 (where R is dot radius and L is dot thickness) Kittel's equation, assuming uniform dynamic magnetization (no pinning at the dot lateral edges), describes the peak position with high accuracy. Analytical calculations and micromagnetic simulations confirmed the gradual evolution of the main mode profile and a smooth transition from the strong to relatively weak pinning conditions with the change of external magnetic field angle.