Prediction of a first-order phase transition in two-dimensional ferromagnets in the presence of random fields
Prediction of a first-order phase transition in two-dimensional ferromagnets in the presence of random fields
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DOI：
10.1016/j.jmmm.2022.169993
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发表时间：
2022-09
影响因子：
2.7
通讯作者：
E. Ibrahim;P. Tang;Shufeng Zhang
中科院分区：
文献类型：
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作者：
E. Ibrahim;P. Tang;Shufeng Zhang
随机磁场通过磁畴的形成抑制了长程磁有序。磁区的大小由交换相互作用、磁各向异性和随机场强度之间的竞争决定。在这里，我们从理论上研究了具有随机磁场的各向异性海森堡模型的二维磁化强度的温度依赖性。我们发现，磁畴的磁化强度呈现一级相变，在临界温度下，磁化强度是不连续的。此外，即使外加磁场的大小小于无序的强度，一级相变仍然存在。上述不同寻常的一阶相变可以用掺杂的二维磁体进行实验验证。
Random magnetic fields suppress the long-range magnetic ordering through the formation of the magnetic domains. The size of the domains is determined by the competition among the exchange interaction, the magnetic anisotropy, and the strength of the random field. Here we theoretically investigate the temperature dependence of the magnetization of the two-dimensional domains for the anisotropic Heisenberg model with a random magnetic field. We find that magnetization of the domains displays a first-order phase transition in which the magnetization is discontinuous at a critical temperature. Moreover, the first-order transition persists even in the presence of an external magnetic field whose magnitude is smaller than the strength of the disorder. The above unusual first-order phase transition can be experimentally tested with doped two-dimensional magnets.