Realistic magnetic thermodynamics by local quantization of a semiclassical Heisenberg model

• Published in: npj computational materials Vol. 8; no. 1; pp. 1 - 6
• Main Authors: Walsh, Flynn, Asta, Mark, Wang, Lin-Wang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30.08.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/1034/1035; 639/301/1034/1037; 639/301/119/997; Antiferromagnetism; Approximation; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computational Intelligence; Critical temperature; Ferromagnetism; Heisenberg theory; Magnetic measurement; Magnetism; Materials Science; Mathematical and Computational Engineering; Mathematical and Computational Physics; Mathematical Modeling and Industrial Mathematics; Monte Carlo simulation; Short range order; Statistical models; Theoretical; Thermodynamics
• ISSN: 2057-3960; 2057-3960
• DOI: 10.1038/s41524-022-00875-8

Classical Monte Carlo simulation of the Heisenberg model poorly describes many thermodynamic phenomena due to its neglect of the quantum nature of spins. Alternatively, we discuss how to semiclassically approach the quantum problem and demonstrate a simple method for introducing a locally approximate form of spin quantization. While the procedure underestimates magnetic short-range order, our results suggest a simple correction for recovering realistic spin–spin correlations above the critical temperature. Moreover, ensemble fluctuations are found to provide reasonably accurate thermodynamics, largely reproducing quantum mechanically calculated heat capacities and experimental magnetometry for ferromagnetic Fe and antiferromagnetic RbMnF 3 . Extensions of the method are proposed to address remaining inaccuracies.