Theoretical study of electrical oscillation effect in Sn2P2Se6 single crystals with incommensurate phase

For the ferroelectric (FE) semiconductor Sn2P2Se6 with the incommensurate (IC) phase the theoretical study of long-term low-frequency (10 Hz - 1 kHz) electric oscillations appeared in a deep IC-phase and acquired the relaxation character in the vicinity of IC-FE phase transition has been performed. A bifurcation analysis was performed by the examination of the evolution equation for the one-dimensional case in the first harmonic approximation with linearization near T-c. Results point out the existence of bifurcation of "saddle --> stable focus --> stable node" type. The oscillatory solution of the nonlinear evolution equation has been found in the region, where we can neglect the relaxation processes. The dispersion relation for the amplitude and the frequency of oscillations has been discussed.