Anion modulation induced room-temperature ferromagnetism in two-dimensional CuCrSe2
Two-dimensional (2D) magnetic materials hold promise for next-generation spintronics, yet most exhibit Curie temperatures (Tc) far below room temperature, limiting practical applications. Here, we report the realization of room-temperature ferromagnetism in CuCrSe2 nanosheets via controlled anion removal achieved by post-synthetic vacuum annealing. Raw CuCrSe2 shows a low Tc of ~120 K, whereas annealed CuCrSe2 (A-CuCrSe2) nanosheets exhibit robust ferromagnetic ordering above 300 K. Structural and compositional analyses, including transmission electron microscopy, Raman spectroscopy, and X-ray absorption spectroscopy, confirm that A-CuCrSe2 retains the original layered crystal structure with an estimated Se vacancy concentration of approximately 10%. Magnetic measurements reveal room-temperature ferromagnetism in exfoliated nanosheets, corroborated by magnetic imaging and electric transport measurements. Anomalous Hall effect (AHE) measurements uncover the coexistence of two ferromagnetic phases within the same sample: one with low Tc (~120 K) and another with high Tc (>300 K), indicating spatially heterogeneous magnetic ordering driven by anion removal distribution. Density functional theory (DFT) calculations elucidate the microscopic mechanism, suggesting that Se vacancies modulate the magnetic exchange interactions, enhancing Tc. This work demonstrates that anion modulation is an effective intrinsic strategy to achieve room-temperature ferromagnetism in 2D materials, potentially advancing spintronic applications.