Transient processes in spin-wave systems with magnetic dipole radiation — II. Experimental investigations

Abstract

The harmonic and anharmonic transient evolutions of the power absorbed by a ferromagnetic system which is suddenly submitted to an electromagnetic excitation of constant amplitude is experimentally studied under perpendicular pumping. We show the influence of the magnetic dipole radiation of the uniform magnons in narrow line-width crystals, like YIG and lithium ferrite, on the transient and steady-state absorption processes. When the ferromagnetic system is overcoupled, the absorbed r.f. power reaches, in the harmonic case the linear steady-state level after an overshoot due to the retardation of the radiation processes with respect to the direct photon-magnon processes of absorption. In the same way, in the anharmonic case, the overcoupled ferromagnetic system leads to a non-linear steady-state absorption level, higher than the steady-state linear level. The experimental results are in good agreement with the theory that we developed earlier; we can deduce from the theory the characteristics of the uniform magnons is the basic mechanism of tunable band pass filters and limiters dipole radiation of the uniform magnons is the basic mechanism of tunable band pass filters and limiters using the ferromagnetic resonance. Expressions are derived for the selectivity of these devices and for the residual energy contained in the spike of the limiters. These expressions are in agreement with the experimental results.