Impact of single crystal properties on nucleation and growth mechanisms of a spin transition

We have investigated the spatio-temporal development of the spin transition in different single crystals of the molecular complex [Fe(bapby)(NCS)(2)] using optical microscopy. The thermal spin transition proceeds by nucleation at macroscopic defects, followed in most cases by anisotropic growth. We show that a lower crystalline quality leads to multi-site nucleation and intermittent spin transitions. We conclude that each crystal of a same spin crossover complex can have its proper spin transition kinetics depending on its crystalline properties and intrinsic microstructure. (C) 2014 Elsevier Ltd. All rights reserved.