Spin-polarized Mn2⁺ emission from mn-doped colloidal nanocrystals

We report magnetophotoluminescence studies of strongly quantum-confined 0D diluted magnetic semiconductors (DMS), realized in Mn2⁺-doped ZnSe/CdSe core-shell colloidal nanocrystals. In marked contrast to their 3D (bulk), 2D (quantum well), 1D (quantum wire), and 0D (self-assembled quantum dot) DMS counterparts, the ubiquitous yellow emission band from internal d-d (T14→A16) transitions of the Mn2⁺ ions in these nanocrystals is not suppressed in applied magnetic fields and does become circularly polarized. This polarization tracks the Mn2⁺ magnetization, and is accompanied by a sizable energy splitting between right- and left-circular emission components that scales with the exciton-Mn sp-d coupling strength (which, in turn, is tunable with nanocrystal size). These data highlight the influence of strong quantum confinement on both the excitation and the emission mechanisms of magnetic ions in DMS nanomaterials.