Above-Room-Temperature Ferromagnetism in Copper-Doped Two-Dimensional Chromium-Based Nanosheets

Two-dimensional ferromagnetic materials (2D-FMs) are expected to become ideal candidates for low-power, high-density information storage in next-generation spintronics devices due to their atomically ultrathin and intriguing magnetic properties. However, 2D-FMs with room-temperature Curie temperatures (T-c) are still rarely reported, which greatly hinders their research progress and practical applications. Herein, ultrathin Cu-doped Cr7Te8 FMs were successfully prepared and can achieve above-room-temperature ferromagnetism with perpendicular magnetic anisotropy via a facile chemical vapor deposition (CVD) method, which can be controlled down to an atomic thin layer of similar to 3.4 nm. STEM-EDX quantitative analysis shows that the proportion of Cu to metal atoms is similar to 5%. Moreover, based on the anomalous Hall effect (AHE) measurements in a six-terminal Hall bar device without any encapsulation as well as an out-of-plane magnetic field, the maximum T-c achieved similar to 315 K when the thickness of the sample is similar to 28.8 nm; even the ultrathin 7.6 nm sample possessed a near-room-temperature T-c of similar to 275 K. Meanwhile, theoretical calculations elucidated the mechanism of the ferromagnetic enhancement of Cu-doped Cr7Te8 nanosheets. More importantly, the ferromagnetism of CVD-synthesized Cu-doped CrSe nanosheets can also be maintained above room temperature. Our work broadens the scope on room-temperature ferromagnets and their heterojunctions, promoting fundamental research and practical applications in next-generation spintronics.