Recent developments on 2D magnetic materials: challenges and opportunities

The emergence of two-dimensional (2D) magnetic materials exhibiting strong magnetization at ultrathin limits above room temperature is promising for miniaturization of devices beyond Moore's law for future energy efficient nanoelectronic devices. Here, the current status, different mechanisms for the existence of magnetism, spin current injection, and other magnetic properties of monolayer to few layers of various 2D magnetic materials are reviewed. Some of the promising applications of these materials are spintronics devices such as spin valves, spin tunnel field-effect transistors, and spin-filtering magnetic tunnel junctions. Due to the tunable electronic properties of these 2D materials, it is quite interesting to inject the spin current with suitable ferromagnetic contacts. For instance, black phosphorus is a layered material with a small Schottky barrier height capable of injecting spin current. This review includes many recently explored 2D magnetic materials ranging from exfoliated 2D crystals to CVD grown materials from single to several layers, demonstrating tunable layer-dependent magnetic properties. We also explore some of the promising theoretical study based on 2D magnetic compounds such as 2D alkali-based chromium chalcogenides, which shows ferromagnetic as well as semiconducting behavior. The layer-dependent magnetic ordering has been observed in layered compounds like 1T-CrTe2, VSe2, CrI3, and Fe3GeTe2, which have great potential for the future applications in magnetic-based electronic devices. Finally, we emphasize the challenges, opportunities, and future directions of the 2D magnetic materials, where new discoveries might have outstanding impact in transformational scientific breakthroughs towards memory, spintronics, optoelectronics, and other multifunctional device applications.