Monte Carlo Simulation Study on Domain Formation in the Photoinduced Low-Spin High-Spin Transition

The domain formation process of the photo-induced cooperative low-spin (LS) to high-spin (HS) conversion phenomena are studied based on the Monte Carlo simulation method. The existence of the threshold light intensity and the incubation period are demonstrated. It is pointed out that the nucleation barrier of HS domain is surmounted by the fluctuation caused by the repetition of excitation and de-excitation. By defining an effective temperature for this fluctuation, the time scale of incubation period is estimated following the usual domain formation theory. It grossly accounts the Monte Carlo (MC) results in three-dimensional cases. The phase separation of HS and LS domain is reproduced by considering the volume striction effect. The step wise abrupt conversion is ascribed to the de-pinning of the volume striction.