Magnetic bistability: From microscopic to macroscopic understandings of hysteretic behavior using ab initio calculations

We study the hysteretic behavior in spin-crossover materials using wave-function ab initio calculations to identify the physical ingredients governing such manifestation. We show that the hysteresis loop is mainly controlled by electrostatic contributions which are here quantified, in contrast with phenomenological descriptions which traditionally rely on the apparent need for intermolecular contacts. A general thermodynamic model based on ab initio information is developed to account for the relevant collective contributions. The magnetic memory appears to be governed by the simultaneous electronic relocalization within the individual constituents and the fluctuation of the Madelung potential difference created by the two spin states. An electronic trapping scenario is suggested to rationalize the hysteresis phenomenon.