Screening magnetic two-dimensional atomic crystals with nontrivial electronic topology

To date, only a few two-dimensional (2D) magnetic crystals have been experimentally confirmed, such as CrI₃ and CrGeTe₃, all with very low Curie temperatures (T_C). High-throughput first-principles screening over a large set of materials yields 89 magnetic monolayers including 56 ferromagnetic (FM) and 33 antiferromagnetic compounds. Among them, 24 FM monolayers are promising candidates possessing T_C higher than that of CrI₃. High T_C monolayers with fascinating electronic phases are identified: (i) quantum anomalous Hall and valley Hall effects coexist in a single material RuCl₃ or VCl₃, leading to a valley-polarized quantum anomalous Hall state; (ii) TiBr₃, Co₂NiO₆, and V₂H₃O₅ are revealed to be half-metals. More importantly, a new type of fermion dubbed type-II Weyl ring is discovered in ScCl. Our work provides a database of 2D magnetic materials, which could guide experimental realization of high-temperature magnetic monolayers with exotic electronic states for future spintronics and quantum computing applications.