Equilibrium, Metastability, and Hysteresis in a Model Spin-crossover Material with Nearest-neighbor Antiferromagnetic-like and Long-range Ferromagnetic-like Interactions

Abstract

Phase diagrams and hysteresis loops were obtained by Monte Carlo simulations and a mean-field method for a simplified model of a spin-crossover material with a two-step transition between the high-spin and low-spin states. This model is a mapping onto a square-lattice $S=1/2$ Ising model with antiferromagnetic nearest-neighbor and ferromagnetic Husimi-Temperley (equivalent-neighbor) long-range interactions. Phase diagrams obtained by the two methods for weak and strong long-range interactions are found to be similar. However, for intermediate-strength long-range interactions, the Monte Carlo simulations show that tricritical points decompose into pairs of critical endpoints and mean-field critical points surrounded by horn-shaped regions of metastability. Hysteresis loops along paths traversing the horn regions are strongly reminiscent of thermal two-step transition loops with hysteresis, recently observed experimentally in several spin-crossover materials. We believe analogous phenomena should be observable in experiments and simulations for many systems that exhibit competition between local antiferromagnetic-like interactions and long-range ferromagnetic-like interactions caused by elastic distortions.

20 pages, 9 figures

References in corpus (6)

• Simple Two-Dimensional Model for the Elastic Origin of Cooperativity among Spin States of Spin-Crossover Complexes
• Realization of the mean-field universality class in spin-crossover materials
• Monte Carlo simulation of pressure-induced phase transitions in spin-crossover materials
• Critical Binder cumulant in two-dimensional anisotropic Ising models
• Structure of Metastable States in Phase Transitions with High-Spin Low-Spin Degree of Freedom
• Monte Carlo Studies of the Ising Antiferromagnet with a Ferromagnetic Mean-field Term

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• Multistability in an unusual phase diagram induced by the competition between antiferromagnetic-like short-range and ferromagnetic-like long-range interactions
• Phase diagrams and free-energy landscapes for model spin-crossover materials with antiferromagnetic-like nearest-neighbor and ferromagnetic-like long-range interactions
• Tunable bifurcation of magnetic anisotropy and bi-oriented antiferromagnetic order in kagome metal GdTi3Bi4
• Density of states for systems with multiple order parameters: a constrained Wang-Landau method
• A plausible mechanism of muscle stabilization in stall conditions
• Spinodal-assisted nucleation in the two-dimensional $q-$state Potts model with short-to-long range interactions
• Critical behaviour near critical end points and tricritical points in disordered spin-1 ferromagnets