Dynamic magnetic and thermodynamic properties of bilayer CrI 3 : a Monte Carlo study

Abstract

Abstract

Abstract Bilayer CrI 3 combines robust intralayer ferromagnetism with weaker, geometry-sensitive interlayer exchange coupling. Its periodically driven response is studied using a spin-3/2 Ising model with separation-dependent interlayer exchange coupling J int (r), intralayer exchange coupling, anisotropy, and a sinusoidal longitudinal field. J int (r) follows a reduced Bethe-Slater form fitted to first-principles energy differences, while finite-temperature behavior is sampled by dynamic Monte Carlo method based on Glauber dynamics with Heat-Bath updates. Changing the layer separation reverses the sign of J int at r c ≈ 6.32Å, switches interlayer alignment from parallel to antiparallel, and brings the dynamic transition temperature to a minimum at J int = 0. Stronger intralayer exchange coupling raises this temperature, whereas more negative anisotropy and larger field amplitude lower it; frequency has little effect. Layer-resolved magnetizations distinguish antiferromagnetic compensation from symmetric field-driven reversal. In the antiferromagnetic regime, interlayer exchange coupling and periodic forcing generate double-loop hysteresis that evolve into a single loop gradually. Under weak driving, ferromagnetic coupling produces a transition-related specific-heat peak and a broader Schottky-like anomaly, whereas antiferromagnetic coupling yields one dominant peak. These results show how intrinsic parameters, thermal fluctuations, and periodic field driving shape the magnetic and thermodynamic properties of the system.