用从头算理论描述磁性材料中相变周围的热效应：电子胶和波动的局部矩
Caloric effects around phase transitions in magnetic materials described by ab initio theory: The electronic glue and fluctuating local moments
摘要：
我们描述了磁，气压和弹热效应（MCES，BCE和eCE）的材料，具有不连续（一阶）和连续（二阶）的磁相变。我们的从头算理论的材料的相互作用的电子在无序的本地时刻（DLMs）产生了明确的机制，这些转变的驱动程序，在这里，我们研究相关的热效应在三个案例研究中，这两种类型的过渡是显而易见的。我们的前期工作描述了FeRh的磁相图和大MCE。在这里，我们提出了其实质性的BCE和eCE的计算。我们描述了镝的MCE，并发现非常好的协议与实验值的等温熵（$ΔS_{iso}$）和绝热温度（$ΔT_{ad}$）的变化在一个大的温度跨度和不同的应用磁场值。我们检查的条件符合克劳修斯-克拉珀龙分析，我们用它来提出一个有前途的弹热冷却循环所产生的熵对温度和双轴应变的不寻常的依赖关系，在我们的第三个案例研究-锰$_3$ GAN反钙钛矿的最佳值的$ΔS_{iso}$和$ΔT_{ad}$。我们解释了如何既$ΔS_{iso}$和$ΔT_{ad}$可以保持大的利用复杂的拉伸应变-温度磁相图，我们早先预测这种材料，并提出磁滞效应将缺席一半的热量循环。这种丰富而复杂的行为源于Mn局部矩之间相互作用的受挫性质。
英文摘要：
We describe magneto-, baro- and elastocaloric effects (MCEs, BCEs and eCEs) in materials which possess both discontinuous (first-order) and continuous (second-order) magnetic phase transitions. Our ab initio theory of the interacting electrons of materials in terms of disordered local moments (DLMs) has produced explicit mechanisms for the drivers of these transitions and here we study associated caloric effects in three case studies where both types of transition are evident. Our earlier work had described FeRh's magnetic phase diagram and large MCE. Here we present calculations of its substantial BCE and eCE. We describe the MCE of dysprosium and find very good agreement with experimental values for isothermal entropy ($ΔS_{iso}$) and adiabatic temperature ($ΔT_{ad}$) changes over a large temperature span and different applied magnetic field values. We examine the conditions for optimal values of both $ΔS_{iso}$ and $ΔT_{ad}$ that comply with a Clausius-Clapeyron analysis, which we use to propose a promising elastocaloric cooling cycle arising from the unusual dependence of the entropy on temperature and biaxial strain found in our third case study - the Mn$_3$GaN antiperovskite. We explain how both $ΔS_{iso}$ and $ΔT_{ad}$ can be kept large by exploiting the complex tensile strain-temperature magnetic phase diagram which we had earlier predicted for this material and also propose that hysteresis effects will be absent from half the caloric cycle. This rich and complex behavior stems from the frustrated nature of the interactions among the Mn local moments.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
