Nonlinear eigenoscillations of spins in a parallel-plane ferromagnetic resonator

Inhomogeneous, with respect to thickness, spin eigenoscillations of arbitra ry amplitude in a ferromagnetic resonator (a film placed in a normal satura ting magnetic field) are investigated theoretically Nonlinear boundary cond itions are derived for the case of arbitrary character and degree of the sp in pinning on the surface. The solutions to the nonlinear dynamical equatio ns for magnetization that describe standing waves in angle variables (prece ssion angle-azimuthal angle) are found. The analysis of solutions on the ph ase plane makes it possible to determine their mode composition and formula te simple algorithms for calculating profiles and spectra. The considered n onlinear oscillations must be excited at high excitation levels when spin-w ave resonance (SWR) is investigated experimentally. The existence of the se ries of modes with a finite excitation threshold (in the case of hard excit ation) is indicated. When the excitation level of the fundamental inhomogen eous mode is increased, its amplitude tends to be distributed uniformly ove r the film thickness. In this case, eigenfrequencies (and fields) undergo a nonlinear shift, which is especially strong when the easy-plane type of an isotropy exists on the surface. As the excitation level increases, the eige nfrequencies (and eigenfields) cease to depend on the boundary conditions.