Stochastic resonance in ferroelectric triglycine sulfate

Stochastic resonance is a phenomenon that occurs in nonlinear systems, wher eby a weak periodic input is amplified by an additional noise. We observed stochastic resonance in ferroelectric Triglycine sulfate (TGS). Below the C urie point there exist two domain slates which are separated by an energeti c barrier. The material is driven by small periodic signals that do not cau se switching. There ore different ways to prove the occurence of stochastic resonance in a bistable system: (i) The response of the system at the inpu t frequency shows a maximum at a special noise level, (ii) An improvement o f the signal-to-noise ratio may be registered. Additionally we observed tha t in ferroelectric TGS there exists a dependence of the response amplitude on the direction of variation of the noise, Increasing the noise from a ver y low level yields a lower maximum response than decreasing the noise. This may be caused by pinning of domain walls.