Dynamical aspects of the photoinduced phase transition in spin-crossover complexes

We report a dynamical study on the photoinduced cooperative changes of the spin configurations in single crystals of the organometal spin-crossover co mplex. In the photoswitching process between low- and high-spin states, non linear characteristics such as thresholdlike behavior, incubation period, a nd phase separation have been observed. These results demonstrate that the cooperative intersystem crossing mediated by spin-lattice interaction plays a key role in the driving process of a new class of nonequilibrium phenome na so called photoinduced phase transition.