Figure 1.

(a) Attributes of 2D magnetic materials. (b) Plotting of transition temperatures and critical fields of representative 2D magnetic materials. (c) Scheme of the working principle and setup of scanning single-spin magnetometry technique. (d) Magnetization maps of monolayer, pentalayer, and nonalayer of CrI₃ at 7 K. Lower row: the data of stray magnetic field B_NV measured across the edges of each flake, along the lines indicated in the maps. (e) Magnetic domain mapping of 250 nm Fe₃GeTe₂ microstructures (diamond and rectangular shape) at 110 K and 300 K, respectively. The data at 110 K exhibits stripe-like feature in the out-of-plane magnetization component for both these two microstructures, while at 300 K, in-plane magnetization component plays a dominant role: a magnetic vortex state in the diamond-shaped microstructure and a multidomain state in the rectangular-shaped microstructure. (f) Overfocused Lorentz TEM images of the skyrmion bubbles of Fe₃GeTe₂ at 93 K and zero field (upper panel) and a zoom-in image of the in-plane magnetization distribution map for the skyrmion bubble outlined by a white dashed box (bottom panel). (g) Underfocused Lorentz TEM images of 70 nm Cr_1/3NbS₂ evolving with in-plane magnetic field at 110 K. Panels (c, d) are reproduced with permission from ref. [16], copyright 2019 Science. Panel (e) is reproduced with permission from ref. [17], copyright 2018 Nano Letters. Panel (f) is reproduced with permission from ref. [21], copyright 2019 Nano Letters. Panel (g) is reproduced with permission from ref. [22], copyright 2012 Physical Review B.