Dynamical limits upon downsizing in thin films of SCO nanocrystals with controlled morphology

Our most recent experiments on ID09 support a scheme whereby the macroscopic volume expansion and spin state switching are separated in time. Such behaviour is different from the expectation that phase transformation only requires atomic displacements in the unit cell, that can occur simultaneously with propagation of a volumic strain. SCO molecules instead remain trapped by local energy barriers separating low spin and high spin states. The observed delay between the volume increase (caused predominantly by lattice heating) and the macroscopic switching may be an indication of a cooperative process during phase separation that takes longer than the switching of independent molecules. This finding motivates an optimised material design, scalable with size dependent dynamics and intrinsic energetics. Here, we propose to study nanocrystals undergoing molecular spin transition in a form of oriented thin films, and exhibiting negligibly small thermal expansion.