2008/02/08 by Carsten Timm, Charles J. Pye
Materials Science · Physics and Astronomy · #Magnetic properties of thin films #Magnetism in coordination complexes #Theoretical and Computational Physics #cond-mat.stat-mech
paper · pdf · doi:10.1103/physrevb.77.214437
7 pages, 5 figures included
arxiv created 2008/02/08 · openalex publication_date 2008/06/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Spin-crossover compounds, which are characterized by magnetic ions showing low-spin and high-spin states at thermally accessible energies, are ubiquitous in nature. We here focus on the effect of an exchange interaction on the collective properties for the case of nonmagnetic low-spin ions, which applies to Fe2+ compounds such as FeO under high pressure. Monte Carlo simulations are used to study a three-dimensional spin-crossover model for the full parameter range from essentially pure high spin to essentially pure low spin. We find that as the low-spin state becomes more favorable, the Curie temperature drops, the universality class deviates from the three-dimensional Heisenberg class, and the transition eventually changes to first order. A heat-bath algorithm that grows or shrinks low-spin and high-spin domains is developed to handle the first-order transition. When the ground state has low spin, a reentrant magnetic transition is found in a broad parameter range. We also observe a percolation transition of the high spins, which branches off the first-order magnetic transition.