Unified dynamical description of pulsed magnetic field and pressure effects on the spin crossover phenomenon

The effects of pulsed magnetic fields and pressure on the spin crossover phenomenon between high-spin and low-spin electronic states in ferrous compounds are investigated by introducing a model based on a macroscopic master equation written in the mean-field approximation. A bidirectional transition is predicted on the spontaneous thermal hysteresis and the light-induced thermal hysteresis (LITH) loops. The model also witnesses that a pressure pulse displays a mirror effect compared to a pulse of magnetic field and that different behaviors can be obtained depending on the intensity and shape of these pulses. In particular, we found that a rather long (similar to 1 s) external perturbation must be used to reach a maximal spin conversion. In addition, the pulse intensity necessary to trigger a transition on the LITH loop is at least 30 times higher than for a spontaneous thermal hysteresis loop. As a final theoretical point, the correlation between the cooperativity and the response to a pulsed excitation is presented.