Relaxation Oscillation near the Threshold of Instability in Yttrium Iron Garnet

Abstract

Coherent low‐frequency relaxation oscillation in the amplitude of the z component of magnetization and the imaginary part of susceptibility has been observed in YIG at a microwave power level slightly above the threshold of instability. The relaxation time associated with the uniform mode has also been measured. The condition for coherent relaxation oscillation depends critically on the magnitude of the dc magnetic field. The low‐frequency oscillation is interpreted to be the beat of two high‐frequency components due to a split in the frequency of the k spin wave ω_k±Δω_k. It is also believed that the period of oscillation is controlled by the relaxation time associated with the uniform mode.