Comparison of static and light-induced thermal hystereses of a spin-crossover solid, in a mean-field approach

We investigate the relationship between the two mean-field models which hav e been proposed independently for characterizing the static and the light i nduced thermal hystereses of spin-transition solids, respectively involving an interaction parameter J and a relaxation self-acceleration parameter a. We unify these two models into a unique-static and dynamic-mean-field desc ription based on Arrhenius thermal activation processes. The model is used to analyse the experimental hysteresis loops, the relaxation curves in the dark, and the light-induced instability in the spin-crossover system [FexCo 1-x(btr)(2)(NCS)(2)]H2O. A linear relationship between J and alphaT is obta ined, which is in qualitative agreement with the available theories.