Photo-induced and Thermal Bistability of Spin Crossover Nano-particles

We predict that the thermal and photo-induced bistability in spin crossover nanoparticles is strongly dependent on the heterostructure geometry of spin crossover (SCO) core-shell nanoparticles. We show that varying the core-shell lattice mismatch allows systematic control of the properties of SCO nanoparticles. We demonstrate a linear relationship between a 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.