Theory, properties and engineering of 2D magnetic materials

Two-dimensional (2D) magnetism with a high Curie temperature (Tc) has been the pursuit of generations for its potential application in spintronic devices. Meanwhile, some intriguing physical properties, including the quantum anomalous Hall effect and skyrmions, have been observed in 2D ferromagnetic materials (2DFMs), which are attractive for applications in highefficiency quantum and memory devices. However, the realization of 2D magnetism by experiments has only been made in the last several years, but the Tc of these 2D materials is extremely low. Therefore, the search for 2D intrinsic ferromagnetic materials with high values of Tc, or enhancing Tc by various modulation methods to inhibit thermal fluctuations, are current active research directions. Here, we present a broad review of recent progress in 2DFMs. The physical background is first illustrated as a prerequisite for a deep understanding of 2DFMs. 2DFMs can have high values of Tc, and machine learning and high-throughput screening can play a vital role in achieving this. Modulation methods to stabilize long-range magnetic order are emphasized from the perspective of symmetry breaking. Finally, some distinctive properties of 2DFMs for device applications are highlighted. The research directions that we propose here will be of great assistance in exploring and understanding novel 2DFMs that can generate new devices in the fields of spintronics and memory devices.