Recent Advances in Two-Dimensional Magnets: Physics and Devices towards Spintronic Applications

Abstract

<jats:p>The emergence of low-dimensional nanomaterials has brought revolutionized development of magnetism, as the size effect can significantly influence the spin arrangement. Since the first demonstration of truly two-dimensional magnetic materials (2DMMs) in 2017, a wide variety of magnetic phases and associated properties have been exhibited in these 2DMMs, which offer a new opportunity to manipulate the spin-based devices efficiently in the future. Herein, we focus on the recent progress of 2DMMs and heterostructures in the aspects of their structural characteristics, physical properties, and spintronic applications. Firstly, the microscopy characterization of the spatial arrangement of spins in 2D lattices is reviewed. Afterwards, the optical probes in the light-matter-spin interactions at the 2D scale are discussed. Then, particularly, we systematically summarize the recent work on the electronic and spintronic devices of 2DMMs. In the section of electronic properties, we raise several exciting phenomena in 2DMMs, i.e., long-distance magnon transport, field-effect transistors, varying magnetoresistance behavior, and (quantum) anomalous Hall effect. In the section of spintronic applications, we highlight spintronic devices based on 2DMMs, e.g., spin valves, spin-orbit torque, spin field-effect transistors, spin tunneling field-effect transistors, and spin-filter magnetic tunnel junctions. At last, we also provide our perspectives on the current challenges and future expectations in this field, which may be a helpful guide for theorists and experimentalists who are exploring the optical, electronic, and spintronic properties of 2DMMs.</jats:p>

Recent Progress in Proximity Coupling of Magnetism to Topological Insulators

“…Recently discovered van der Waals magnetic materials (MMs), [ 184,185 ] that is, layered materials which contain 2D sheets of magnetic materials stacked with van der Waals forces, have brought a paradigm shift in heterostructures of ferromagnetic materials, opening the possibility of van der Waals heterostructures [ 186–188 ] incorporating magnetism. According to theoretical calculations, ferromagnetism can be realized in several types of layered transition metal compounds, including transition metal trichalcogenides (CrGeTe 3 , CrSiTe 3 , etc.…”

“…Spintronics exploits the electron's spin for both data storage and processing of logic operations. [ 185,242,243 ] Logical states (0 and 1) are represented by magnetization configurations, for example, polarization of the electron spins in a conductor, the direction of magnetization of a ferromagnet, or topological charge of a skyrmion. These states are generally isoenergetic, which in principle can allow switching between states with very little wasted energy.…”

Atomically Thin Quantum Spin Hall Insulators

“…Further detail on the field of spintronics and its applications, spin and charge interconversion by other quantum materials like 3D topological insulators, Rashba interfaces, ultrathin Dirac and Weyl semimetals, superconductors, and non‐collinear ferromagnets, as well as advances in 2D materials for spintronics applications can be found in these comprehensive reviews by Wolf et al., [ 229 ] Han et al., [ 41 ] Hirohata et al., [ 230 ] Ningrum et al., [ 231 ] and Ahn. [ 232 ]…”

Electronic and Magnetic Characterization of Epitaxial CrBr3 Monolayers on a Superconducting Substrate

“…This means that one can—for example—imprint magnetic properties of 2D magnets to the other layers without modifying their intrinsic properties and create novel spintronic and magnonic devices. [ 8–10 ] This designer concept can be utilized in systems combining magnetism with superconductivity to realize topological superconductivity. [ 11,12 ] It is currently attracting intense attention due to its potential role in building blocks for Majorana‐based qubits for topological quantum computation.…”