Oscillations and Period-Doubling of Magnon Amplitude under Parallel Pumping in Antiferromagnetic CuCl₂2H₂O

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Oscillations of magnon amplitude under intense parallel pumping have been observed in antiferromagnetic CuCl₂2H₂O at the microwave power of P⁄P_c>12 dB, where P is the incident microwave power and P_c the threshold one for spin-wave instability. The measurements have been done at the temperature of 1.4 K and at the pumping frequency of 8.91 GHz. The fundamental frequency at the static magnetic field of 6300 Oe is 3.5 MHz at P⁄P_c=13.0 dB and increases gradually with increasing P. With increasing pumping field it occurs subharmonics which is attributed to period-doubling bifurcations known as a route to chaos.