Threshold effect of microwave power on ferromagnetic resonance in $\mathrm{K_{0.4}[Cr(CN)_6][Mn(S)\text{-}pn](S)\text{-}pnH_{0.6}}$ single crystals

A stepwise change in the ferromagnetic resonance spectrum in a $\mathrm{K_{0.4}[Cr(CN)_6][Mn(S)\text{-}pn](S)\text{-}pnH_{0.6}}$ chiral magnet has been observed in a critical microwave magnetic field of $1.8$ Oe. The threshold changes in the ferromagnetic resonance spectra are caused by Suhl instability leading to the generation of defects of the magnetic structure, chiral spin solitons. The threshold effect is not observed in the same microwave range in similar chiral crystals $\mathrm{[Cr(CN)_6][Mn(S)\text{-}pnH(H_2O)](H_2O)}$ with a stronger Heisenberg exchange interaction.