Nanosecond study of spin state transition induced by a single nanosecond laser shot on [Fe(NH2trz)3] compounds inside and outside their thermal hysteresis loops

► We propose a novel experimental set-up that records in real time and with a nanosecond time resolution the kinetics of photo-induced phase transitions. ► The experiments performed on two different spin crossover compounds make it possible to follow the evolution of the sample within its phase diagram. ► At room temperature, the phase transition is driven by the laser induced heating.