Giant Zeeman Splitting for Monolayer Nanosheets at Room Temperature

Giant Zeeman splitting and zero-field splitting (ZFS) are observed in 2D nanosheets that have monolayers of atomic thickness. In this study, single-crystalline CdSe­(ethylenediamine)0.5 and Mn2+-doped nanosheets are synthesized via a solvothermal process. Tunable amounts of Mn2+(0.5–8.0%) are introduced, resulting in lattice contraction as well as phosphorescence from five unpaired electrons. The exciton dynamics are dominated by spin-related electronic transitions (4T1 → 6A1) with long lifetimes (20.5, 132, and 295 μs). Temperature-varied EPR spectroscopy with spectral simulation reveals large ZFS (D = 3850 MHz) due to axial distortion of substituted Mn2+ (S = 5/2). In the magnetic circular dichroism (MCD) measurements, we observed giant Zeeman splitting with large effective g values (up to 231 ± 21), which implies huge sp–d exchange interactions in 2D monolayer regimes, leading to diluted magnetic semiconductor (DMS) materials.