In the previous sections a couple of typical vdW spintronic devices such as spin valves, spin filter tunnel junctions, and planar spin FET have been introduced, and we now come to a brief discussion on several other configurations of spintronic devices using vdW magnets as a platform. In Fig. 6, a variety of nanostructures for vdW spintronics are illustrated. It can be seen that spin-related electronic devices can in principle be built via a mechanical stacking method, giving rise to possible applications such as 2D heterostructure of multi-ferroics, vdW magnetic recording, and topological magnetic states, etc. Up to now, the emerging phenomena in 2D vertical multi-ferroics as well as topological magnetic states in the vdW systems are attracting great interests. We now propose a roadmap for exfoliated spintronics, as indicated in Fig. 7. In short, depending on the development of vdW materials, the future trend of the vdW spintronics can be classified into fundamental- and application-oriented directions.
For fundamental research, the future tasks will be looking for new emerging phenomena including topological magnetic states (Skyrmion as an example), magnetic semiconductors and the associated devices such as magnetic p–n junctions, 2D multi-ferroic devices via the stacking of vdW layered materials, the novel devices for superconducting spintronics (such as Pi junction, etc.) based on vdW magnets, novel interfacial coupling using layered FM/AFM compounds, as well as NMR/ESR and Rashba effects in 2D vdW systems.
For application research, the top priority will be to find room temperature vdW magnets. And the mission for future application shall include spin torque transfer (or spin Hall related) devices, spin diodes, spin valves, vdW magnetic semiconductors (as compared to the bulk diluted magnetic semiconductors[129–133]), magnetic electronic sensors, data storage devices (such as optical/electrical writing of domains, exchange bias effects that may be gate tunable, magnetic vdW electronics for biological utilities, etc.).
Finally, we would like to recall the fact that, in principle, vdW magnetic materials are compatible with mass production processes such as CVD methods. For example, CVD grown non-vdW magnetic thin films have been demonstrated recently[31, 32]. It is reasonable to believe that flexible spintronics can be realized in the very near future. Layered magnetic materials thus hold great promises for spintronics made in a totally new manner, i.e., atomic layer by atomic layer, with an infinite combination of the rotation angle, and unlimited possibility of assembling sequence, that will truly revolutionize our daily life.