Iron-based ferromagnetic van der Waals materials

Two-dimensional magnets with high Curie temperatures have recently been produced by incorporating the prototypical ferromagnetic element, iron, into 2D van der Waals layers using the iron-based layered compounds known as Fe x GeTe2 (x = 3, 4, 5). In these materials, each layer consists of an Fe x Ge slab sandwiched by chalcogen tellurium (Te) atoms and the layers are stacked by van der Waals interactions. Their intrinsically high Curie temperatures, as high as room temperature, and large magnetization have drawn significant attention. Moreover, their ability to be tuned using their extrinsic parameters, such as gating and doping, makes their application in spintronics promising. Since they are primarily metallic materials with high electrical conductivity, it is easy to characterize their transport properties and thus directly use them for spintronic devices. In this review, we summarize the magnetic properties of layered iron-based magnetic materials and the spin transport phenomena in devices made of these materials, and provide perspective and insight into the characteristics of these unique materials.