Two-variable macroscopic model for spin-crossover solids: Static and dynamic effects of the correlations

Abstract:

In order to investigate the role of nearest neighbors correlations in the relaxation of the High Spin fraction in spin crossover compounds, we have developed a two macro-variable dynamical model based on Kubo's treatement of the master equation. This is compared to the local equilibrium approach, where short-range correlations are assumed to follow adiabatically the long range-order parameter. The sigmoidal shape of the relaxation, previously associated with the effects of interactions, and the so-called “tail effect”, i.e. the extra-slowing down at long times due to the correlations are obtained. The accurate comparison to experimental relaxation data confirms the coexistence of short-range and long-range interactions in spin-crossover solids.