Instability of Nonlinear Ferromagnetic Resonance

The results of a theoretical and experimental investigation of the problem of nonlinear ferromagnetic resonance (NFMR) are given. It is shown that the NFMR instability is a fundamental property and takes place with Bloch's mechanism of magnetic-moment relaxation. Characteristics of automodulation oscillations (which accompany the NFMR) are briefly described. It is shown that in parametric ferrite amplifiers (PFA) and limiters the NFMR instability leads to the occurrence of nonthermal noise, and in PFA causes the autosuppression of amplification. Observations are reported of ``spike'' electromagnetic emission and nonstationary retarded reradiation, which cannot be explained in the framework of previously developed theory.