Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters
Effect of Single-Ion Anisotropy on Magnetocaloric Properties of Frustrated Spin-s Ising Nanoclusters
复制标题
单离子各向异性对受阻自旋伊辛纳米团簇磁热性质的影响
作者：
M. Mohylna;M. Zukovic
用精确计数法研究了自旋s ≥1的反铁磁三角形Ising团簇的磁热性质，研究了单离子各向异性对磁热性质的影响.结果发现，包括单离子各向异性参数D可以导致一个更复杂的基态行为，这也反映在有限温度下的磁热效应（MCE）。对于负D（易平面各向异性）随着s的增加，基态磁化强度作为外场的函数逐渐显示出越来越多的各种高度的高原。除了D<D0≤0的整数s的情况外，第一磁化平台具有非零高度。这种性质有助于在绝热退磁过程中以温度突然下降的形式增强MCE，因为磁场消失到零。在具有较大s和D>0（易轴各向异性）的系统中，冷却速率可以显著增强，尽管其对这些参数的依赖性强烈依赖于团簇的几何形状。从所研究的系统中，在2CS集群中发现了观察巨型MCE的更有利条件，该集群由两个角共享四面体组成，其实验实现可以在技术上用于超低温的高效制冷。
Effects of a single-ion anisotropy on magnetocaloric properties of selected spin-s≥1 antiferromagnetic Ising clusters with frustration-inducing triangular geometry are studied by exact enumeration. It is found that inclusion of the single-ion anisotropy parameter D can result in a much more complex ground-state behavior, which is also reflected in a magnetocaloric effect (MCE) at finite temperatures. For negative D (easy-plane anisotropy) with increasing s, the ground-state magnetization as a function of the external field gradually shows increasing number of plateaus of various heights. Except for the cases of integer s with D<D0≤0, the first magnetization plateau is of non-zero height. This property facilitates an enhanced MCE in the adiabatic demagnetization process in the form of an abrupt decrease in temperature as the magnetic field vanishes to zero. The cooling rate can be considerably enhanced in the systems with larger s and D>0 (easy-axis anisotropy), albeit its dependence on these parameters is strongly dependent on the cluster geometry. From the studied systems more favorable conditions for observing a giant MCE were found in the 2CS cluster, consisting of two corner-sharing tetrahedra, the experimental realization of which could be technologically used for efficient refrigeration to ultra-low temperatures.