Designing two-dimensional materials with magnetic and topological properties has continuously attracted intense interest in fundamental science and potential applications. Here, on the basis of first-principles calculations, we predict the coexistence of antiferromagnetism and Dirac nodal loops (NLs) in monolayer MnB, where the band crossing points are very close to the Fermi level. Remarkably, a moderate strain can induce an antiferromagnetic to ferromagnetic phase transition, driving monolayer MnB to a ferromagnetic metal with Weyl NLs. Such a type of topological quantum phase transition has not been observed before. In addition, the symmetry-protected properties of the two types of NLs as well as the magnetic critical temperatures are investigated. The controllable magnetic and topological order in monolayer MnB offers a unique platform for exploring topological quantum phase transitions and realizing nanospintronic devices.

中文翻译：

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单层 MnB 中的应变可调磁性和节点环

设计具有磁性和拓扑特性的二维材料不断引起基础科学和潜在应用的浓厚兴趣。在这里，基于第一性原理计算，我们预测了单层 MnB 中反铁磁性和狄拉克节点环 (NL) 的共存，其中带交叉点非常接近费米能级。值得注意的是，适度的应变可以诱导反铁磁到铁磁相变，将单层 MnB 驱动为具有 Weyl NLs 的铁磁金属。以前从未观察到这种拓扑量子相变。此外，研究了两种类型的 NL 的对称保护特性以及磁临界温度。