The first-order reversal curves (FORC) diagram method is applied here to the light-induced thermal hysteresis of spin-crossover compounds. Due to the kinetic nature of the photoinduced process, the FORC analysis has been mainly focused on the dependence of the FORC diagram with respect to the temperature sweep rate. Most of the features experimentally observed are explained by adequate simulations using the mean-field macroscopic master equation of a two-level system.

We discuss the influence of the embedding matrix on the thermal hysteretic behavior of spin transition microparticles of Fe(phen)₂(NCS)₂ by using a series of experimental first order reversal curves (FORCs). The shape of FORCs supports the hypothesis considering additional interactions between the spin-transition microparticles and the embedding matrix, which compares to a negative pressure on the particles. A mean-field approach based on negative variable external pressures, together with a cut off/switch on of particles-matrix interactions accounts for the experimental features.