Intrinsic Van Der Waals Magnetic Materials from Bulk to the 2D Limit: New Frontiers of Spintronics

Abstract

2D van der Waals (vdW) magnets, which present intrinsic ferromagnetic/antiferromagnetic ground states at finite temperatures down to atomic‐layer thicknesses, open a new horizon in materials science and enable the potential development of new spin‐related applications. The layered structure of vdW magnets facilitates their atomic‐layer cleavability and magnetic anisotropy, which counteracts spin fluctuations, thereby providing an ideal platform for theoretically and experimentally exploring magnetic phase transitions in the 2D limit. With reduced dimensions, the susceptibility of 2D magnets to a large variety of external stimuli also makes them more promising than their bulk counterpart in various device applications. Here, the current status of characterization and tuning of the magnetic properties of 2D vdW magnets, particularly the atomic‐layer thickness, is presented. Various state‐of‐the‐art optical and electrical techniques have been applied to reveal the magnetic states of 2D vdW magnets. Other emerging 2D vdW magnets and future perspectives on the stacking strategy are also given; it is believed that they will excite more intensive research and provide unprecedented opportunities in the field of spintronics.

Proximity Spin–Orbit Torque on a Two-Dimensional Magnet within van der Waals Heterostructure: Current-Driven Antiferromagnet-to-Ferromagnet Reversible Nonequilibrium Phase Transition in Bilayer CrI3

“…Such current-induced FM phase is stable in-between two pulses, on the proviso that A ⊥ > J 12 in Eq. (7), and can be reversed back to the AFM phase by the next pulse [ Fig. 4(b) and movie in the SM [40]].…”

“…Introduction.-The recent discovery of twodimensional (2D) magnets derived from layered van der Waals (vdW) materials [1,2] has opened new avenues for basic research on low-dimensional magnetism [3,4] and potential applications in spintronics [5][6][7][8][9]. Their magnetic phases can substantially differ from those in conventional bulk magnetic materials due to large structural anisotropy which makes possible different sign and magnitude of intralayer J intra and interlayer J inter exchange coupling between localized magnetic moments.…”

Strain-induced phase transition in CrI3 bilayers

“…The superexchange mechanism which favors FM ordering is more important than the direct interaction between Cr atoms 14 . In CrCl 3 the spins are aligned parallel to the layers plane while in CrBr 3 and CrI 3 the direction of the spins is perpendicular to the plane 15 . The spin-orbit coupling of the halides increases with the size of the atom and this has been identified as the origin of the magnetic anisotropy 16 .…”

Families of magnetic semiconductors — an overview

“…Another class of materials that attract considerable attention are van der Waals magnetic semiconductors studied down to the atomically thin limit [9] . A competition between ferromagnetic and antiferromagnetic superexchange accounts for the magnetic properties of CrI 3 and related systems as a function of the number of layers, electric field, and strain [9,10] .…”