Evidence for Mn$^{2+}$ fine structure in CdMnSe/ZnSe quantum dots caused by their low dimensionality

The axial fine structure with strong positive zero-field splitting for Mn$^{2+}$ ions in CdMnSe/ZnSe quantum dots caused by their low dimensionality was revealed. Magnetic resonance was measured as a variation of photoluminescence intensity. In spite of isotropic $g$ factor of Mn$^{2+}$ ions, the anisotropic behavior of the center of gravity of the resonance has been observed because of the high Boltzmann factor at 35 GHz and 2 K.