2015/10/31 by P. A. Rikvold, Per Arne Rikvold, G. Brown +6 · 26 citations
Materials Science · Physics and Astronomy · #Antiferromagnetism #Condensed matter physics #Ferromagnetism #Ising model #Magnetism in coordination complexes #Metastability #Monte Carlo method #Organic and Molecular Conductors Research #Phase (matter) #Phase diagram #Physics #Quantum mechanics #Spin crossover #Square lattice #Theoretical and Computational Physics #cond-mat.mtrl-sci #cond-mat.stat-mech #k-nearest neighbors algorithm
paper · pdf · doi:10.1103/physrevb.93.064109
published in Physical review. B./Physical review. B 93(6) (American Physical Society) · 20 pages, 9 figures
openalex publication_date 2016/02/16 · arxiv created 2016/02/27 · arxiv updated 2016/03/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
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 end points 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.