Photo-induced and thermal bistability of spin crossover nanoparticles

We predict that the thermal and photo-induced bistability in spin crossover (SCO) core-shell nanoparticles is strongly dependent on the heterostructure geometry. We show that varying the core-shell lattice mismatch allows systematic control of the properties of SCO nanoparticles. We demonstrate a linear relationship between the temperature characterising the photo-induced bistability, T_LIESST, and the thermal spin crossover temperature, T_1/2. This nanostructural approach complements the traditional approach of controlling the relationship between T_LIESST and T_1/2 by making chemical substitutions within families of SCO materials. We give a simple explanation of both relationships. We also demonstrate a non-monotonic dependence of thermal hysteresis width on the shell thickness, which explains a number of apparently contradictory experimental observations.