Air-stable ultrathin Cr3Te4 nanosheets with thickness-dependent magnetic biskyrmions

Two-dimensional (2D) materials with intrinsic magnetism have drawn intense interest for fundamental research and potential application in spintronics and valleytronics. Here we synthesized 2D Cr3Te4 nanosheets with controllable thickness by chemical vapor deposition approach. Reflection magnetic circular dichroism and magneto-transport measurements demonstrated that the Cr3Te4 nanosheets feature excellent environmental stability and have a thickness-dependent ferromagnetic behavior with a high Curie temperature of 165–235 K. Lorentz transmission electron microscopy studies revealed topologically nontrivial magnetic-spin states in the ultrathin Cr3Te4 nanosheets. The magnetic stripe domains in Cr3Te4 can transform into biskyrmion bubbles when an external magnetic field is applied perpendicularly to the nanosheet. The size and density of the biskyrmions can be tuned by the external applied magnetic field and thickness of the nanosheets, respectively. Our findings of topologically nontrivial magnetic-spin states in air-stable 2D magnets could promise new designs of magnetic memory storage, sensors, and spintronics.