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

Abstract

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 $(\sim 1\mathrm{s})$ 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.