二维Ising单层和双层结构中磁热效应的普适标度
Universal Scaling of the Magnetocaloric Effect in 2D Ising Monolayers and Bilayer
浏览论文内容
中文总结 AI 辅助
本研究通过蒙特卡洛模拟六种二维Ising晶格的磁热效应，发现磁熵变等物理量经标度后呈现不依赖配位数与层数的普适行为，为磁制冷剂设计提供依据。
中文摘要 AI 辅助
我们通过蒙特卡洛模拟研究了正方形、蜂窝形和三角形晶格上二维铁磁Ising模型的磁热效应（MCE），涵盖单层和双层构型。采用Binder累积量分析确定了每种结构的临界温度（$T_c$），发现$T_c$随配位数增加而升高，从蜂窝晶格（配位数$r=3$）到三角晶格（配位数$r=6$）依次递增。与之相反，磁熵变（$-ΔS_M$）随配位数增加而减小，在蜂窝晶格中达到最大值。\n将$-ΔS_M$和场指数$n$以各自的峰值归一化并进行适当的温度标度后，在固定低场下，不同磁场强度以及全部六种晶格结构的结果均坍缩到普适主曲线上，证明了MCE存在不依赖于配位数和层数的普适标度行为。临界标度分析进一步支持了观测到的普适性和幂律行为。与$-ΔS_M$不同，绝热温度变化（$ΔT_{ad}$）随配位数增加而增大，而磁格林艾森参数（$Γ_M$）的变化趋势与$-ΔS_M$一致。\n尽管$-ΔS_M$的峰值随配位数增加而降低，但由于$-ΔS_M$曲线的展宽起到补偿作用，相对制冷功率和制冷容量几乎保持不变。$-ΔS_M$、相对制冷功率和制冷容量的磁场依赖关系在约2.6 T（假设交换耦合$J\thickapprox1$ meV）范围内遵循幂律。磁滞分析表明，配位数更低的晶格其磁滞回线宽度随温度升高的衰减速度更快。这些结果确立了二维单层和双层磁性晶格中磁热效应的普适标度行为，为磁性制冷剂的设计提供了指导。
英文摘要
We report a Monte Carlo study of the magnetocaloric effect (MCE) in two-dimensional ferromagnetic Ising models on square, honeycomb, and triangular lattices with monolayer and bilayer configurations. Using Binder cumulant analysis, we determine the critical temperature ($T_c$) of each structure and find that $T_c$ increases with coordination number, from the honeycomb ($r=3$) to the triangular ($r=6$) lattice. In contrast, the magnetic entropy change ($-ΔS_M$) decreases with coordination number, reaching its maximum for the honeycomb lattice. After normalization by their peak values and appropriate temperature scaling, both $-ΔS_M$ and the field exponent $n$ collapse onto universal master curves for different magnetic fields and across all six lattice structures at a fixed low field. This demonstrates universal MCE scaling independent of coordination number and layer count. Critical scaling analysis further supports the observed universality and power-law behavior. Unlike $-ΔS_M$, the adiabatic temperature change ($ΔT_{ad}$) increases with coordination number, whereas the magnetic Grüneisen parameter ($Γ_M$) follows the same trend as $-ΔS_M$. Although the peak value of $-ΔS_M$ decreases with coordination number, the relative cooling power and cooling capacity remain nearly unchanged due to compensating broadening of the $-ΔS_M$ curves. The field dependence of $-ΔS_M$, relative cooling power, and cooling capacity follows power laws up to $\sim2.6$ T (assuming $J\approx1$ meV). Hysteresis analysis shows that lattices with lower coordination numbers exhibit a faster reduction in loop width with increasing temperature. These results establish the universal scaling behavior of the magnetocaloric effect in two-dimensional monolayer and bilayer magnetic lattices and provide guidelines for designing magnetic refrigerants.
