Research advances in two-dimensional non-layered magnetic materials

Two-dimensional (2D) magnetic materials refer to nanomaterials with an extremely thin thickness that can maintain long-range magnetic order. These materials exhibit significant magnetic anisotropy, and due to the quantum confinement effect and high specific surface area, their electronic band structures and surface states undergo remarkable changes. As a result, they possess rich and tunable magnetic properties, showing great application potential in the field of spintronics. The 2D magnetic materials include layered materials, where layers are stacked by weak van der Waals forces, and non-layered materials, which are bonded via chemical bonds in all three-dimensional directions. Currently, most of researches focus on 2D layered materials, but their Curie temperatures are generally much lower than room temperature, and they are always unstable when exposed to air. In contrast, the non-layered structure enhances the structural stability of the materials, and the abundant surface dangling bonds increase the possibility of modifying their physical properties. Such materials are attracting increasing attention, and significant progress has been made in their synthesis and applications. This review first systematically summarizes various preparation methods for 2D non-layered magnetic materials, including but not limited to ultrasound-assisted exfoliation, molecular beam epitaxy, and chemical vapor deposition. Meanwhile, it systematically reviews the 2D non-layered intrinsic magnetic materials obtained in various types of materials in the past five years, as well as a series of novel physical phenomena emerging under the ultrathin limit, such as thickness-dependent magnetic reconstruction dominated by quantum confinement effects and planar topological spin textures induced by 2D structures. Furthermore, it also discusses the critical role played by theoretical calculations in predicting new materials through high-throughput screening, revealing microscopic mechanisms by analyzing magnetic interactions, as well as some important methods of modifying magnetism. Finally, from the perspectives of material preparation, physical mechanisms, device fabrication, and theoretical calculations, the current challenges in the field are summarized, and the application potential and development directions of 2D non-layered magnetic materials in spintronic devices are prospected. This review aims to provide comprehensive references and scientific perspective for researchers engaged in this field, thereby promoting further exploration of the novel magnetic properties of 2D non-layered magnetic materials and their applications in spintronic devices.