TRANSIENT PROCESSES IN SPIN-WAVE SYSTEMS WITH MAGNETIC DIPOLE RADIATION .I. THEORY

The transient evolution of the spin-wave populations is studied in detail under perpendicular pumping, in the linear case and in the non-linear case with three-magnon processes. Calculations are derived taking into account of the variation with time of the dipolar radiation of the uniform magnons which produce reverse magnon → photon transitions. We define the transient growth of the uniform and parametric states on the second quantization basis of the ferromagnetic system, and the electromagnetic field, in the case where coincidence condition is satisfied. From the expressions of the field radiation and the transient power absorbed by the ferromagnetic crystal, we discuss the validity of the theory, showing the importance of the dipolar radiation of the uniform magnons. © 1969.