标题： 铁磁薄膜动态相变中的临界行为交叉 显示英文标题

标题： Crossover of Critical Behavior in Dynamic Phase Transitions of Ferromagnetic Thin Films

摘要： 我们通过动力伊辛模型的蒙特卡罗模拟，研究了铁磁薄膜中动态相变（DPT）的临界行为的交叉现象，重点研究了在时变外部磁场下动态序参量的标度行为。 具体而言，我们研究了这种薄膜系统的临界行为从二维（2D）到三维（3D）的转变，作为薄膜厚度和临界点距离的函数，这使得可以观察到维度交叉现象。 我们的结果表明，有效临界指数表现出其标度行为的明显转变，较薄的薄膜表现出2D特性，而较厚的薄膜则表现出3D行为，这适用于DPT和热力学相变（TPT）。 定量上，与TPT相比，DPT的2D到3D行为的交叉发生在更大的薄膜厚度下，这表明DPT和TPT由明显不同的长度尺度和潜在的表面效应所支配。 这些发现与超薄Co薄膜中的实验观察一致，在其中发现了动态和热力学临界指数的不同。 因此，我们的研究为由时变磁场驱动的薄膜铁磁体中的临界现象提供了深入的解释。 通过比较TPT和DPT的维度交叉特性，我们全面理解了薄膜几何结构和表面效应对非平衡系统中标度定律和临界行为的影响。 显示英文摘要

摘要： We investigate the crossover of critical behavior for the dynamic phase transition (DPT) in ferromagnetic thin films using Monte Carlo simulations of the kinetic Ising model, focusing on the scaling behavior of the dynamic order parameter under a time-dependent external magnetic field. Specifically, we study the transition of the critical behavior of such film systems from two-dimensional (2D) to three-dimensional (3D) as a function of the film thickness and the distance to the critical point, which enables dimensional crossover observations. Our results indicate that the effective critical exponents exhibit a clear transition in their scaling behavior, with thinner films showing 2D-like characteristics and thicker films displaying 3D-like behavior, for both the DPT and the thermodynamic phase transitions (TPT). Quantitatively, the crossover from 2D to 3D behavior occurs at larger film thicknesses for the DPT compared to the TPT, suggesting that DPT and TPT are governed by distinctly different length scales and underlying surface effects. These findings are in agreement with experimental observations in ultrathin Co films, where dynamic and thermodynamic critical exponents were found to differ. Therefore, our study provides an in-depth explanation for critical phenomena in thin-film ferromagnets driven by a time-dependent magnetic field. By comparing the dimensional crossover properties of both TPT and DPT, we present a comprehensive understanding of how thin-film geometry and surface effects influence the scaling laws and critical behavior in nonequilibrium systems.