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.