Zimmer F M, Mourão R, Schmidt M, Tumelero M A, Magalhaes S G
Instituto de Física, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil.
Departamento de Física, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil.
J Phys Condens Matter. 2023 May 10;35(31). doi: 10.1088/1361-648X/acd040.
In this work, we theoretically demonstrate that a strong enhancement of the magnetocaloric effect is achieved in geometrically frustrated cluster spin-glass systems just above the freezing temperature. We consider a network of clusters interacting randomly which have triangular structure composed of Ising spins interacting antiferromagnetically. The intercluster disorder problem is treated using a cluster spin glass mean-field theory, which allows exact solution of the disordered problem. The intracluster part can be solved using exact enumeration. The coupling between the inter and intracluster problem incorporates the interplay between effects coming from geometric frustration and disorder. As a result, it is shown that there is the onset of cluster spin glass phase even with very weak disorder. Remarkably, it is exactly within a range of very weak disorder and small magnetic field that is observed the strongest isothermal release of entropy.
在这项工作中，我们从理论上证明，在几何受挫的团簇自旋玻璃系统中，刚好高于冻结温度时，磁热效应会得到强烈增强。我们考虑由反铁磁相互作用的伊辛自旋组成的具有三角形结构的团簇随机相互作用的网络。使用团簇自旋玻璃平均场理论来处理团簇间无序问题，该理论允许对无序问题进行精确求解。团簇内部分可以用精确枚举法求解。团簇间和团簇内问题之间的耦合体现了几何受挫和无序所带来的效应之间的相互作用。结果表明，即使无序非常弱，也会出现团簇自旋玻璃相。值得注意的是，正是在非常弱的无序和小磁场范围内，观察到了最强的等温熵释放。
