Dynamical Properties of Spin‐Crossover Solids Within the Kinetic Spin‐1 BEG Model in the Presence of a Time‐Dependent Magnetic Field

Abstract

Spin-crossover (SCO) and Prussian blue analogs (PBAs) materials are investigated in 2D with a three-state Blume-Emery-Griffiths (BEG) model where each spin interacts with its nearest neighbors (nn) and may be either in high-spin (HS) or low-spin (LS) state. The interactions through the system lattice are temperature-dependent to account for spin-phonon interactions. The system is also in contact with an oscillating magnetic field energy. The generated numerical results by the dynamic mean field theory (DMFT) study approach are consistent with those derived by kinetic Monte Carlo (KMC) simulations with Glauber dynamics and Arrhenius transition rates. First-order transitions with thermally induced hysteresis phenomena have been observed. Near the hysteresis loops, the model exhibits throughout relaxation curves, some fluctuations in the LS phase, strengthened by increasing temperature where this phenomenon becomes temperature-and magnetic field-dependent.

Magnetic phase transitions in an electroelastic model for magnetically ordered spin-crossover solids

“…Indeed, the total exchange like interaction, J, depends on the nn distance between the SCO sites, and therefore at fixed temperature, T , its average value, < J >= J 0 − α < d > −R HH eq is clearly temperaturedependent. This makes the study of the magnetic subsystem more complex than thought, and in the same time this fact makes the problem extremely close to the previous BEG studies [47,[78][79][80] in which all interacting parameters, including magnetic exchange, were assumed to be linearly depend on temperature.…”

“…where H elec stands for the electronic contribution of ligand-field energy which is set to the value, ∆ = 450 K, and entropy contribution k B T ln (g) which stabilizes the HS state [47,49,[77][78][79][80]:…”

“…In this work, materials combining the spin-transition phenomenon with ferromagnetic interactions are investigated. Describing this particular SCO systems, we used the Blume-Emery-Griffiths (BEG) models [47][48][49] in which we accounted for the elastic and magnetic interactions [34,[50][51][52][53][54][55][56][57][58][59][60][61][62]. We demonstrate that the magnetic and elastic interactions generate tremendous changes in the spin-transition properties, leading to bring to light new and unprecedented non-linear behaviors of the HS fraction, n HS .…”