Saturation of Parallel-Pumped Magnons in the Two-Dimensional Ferromagnets K₂CuF₄ and (CH₃NH₃)₂CuCl₄

Abstract

Parallel pumping of magnons in the two-dimensional ferromagnets K₂CuF₄ and (CH₃NH₃)₂CuCl₄ has been studied at a pumping frequency of 8.91 GHz and T=1.4 K. Both the real and the imaginary components of nonlinear susceptibility, χ′ and χ″, of the parallel-pumped magnons with wave number from 0 to the Brillouin-zone-boundary have been measured up to 25 dB in power beyond the threshold for spin-wave instability. The principal mechanism to limit the amplitude of the parallel-pumped magnons is attributed to the nonlinear damping due to an increase of the magnon interaction between the parallel-pumped magnons.