Generation of 2D nonlayered ferromagnetic VO2(M) nanosheets induced by strain engineering of CO2

Two-dimensional (2D) nonlayered ferromagnets displaying high Curie temperatures, sizable magnetic anisotropy levels, and large spin polarizations are emerging as promising 2D ferromagnetics. However, the difficulties in synthesizing 2D nonlayered intrinsic ferromagnets have largely limited their development. Herein, defect-rich 2D nonlayered VO2(M) nanosheets have been fabricated by deploying straining engineering of CO2 on the metal–insulator transition (MIT) of VO2. Above TMIT, the strong strain engineering of CO2 in the R phase of VO2 generated a very large number of atomic defects in its 3D crystal structure, and as a result facilitated conversion of the defective 3D network to 2D nanosheets along the c-axis. The as-prepared 2D defective VO2(M) nanosheets displayed unique room-temperature ferromagnetism, attributed to the symmetry breaking triggered by the disordered atomic structure combined with the 3D-to-2D transformation.