Propagation effect on photoluminescence of spin-aligned high-density exciton magnetic polarons in Cd0.8Mn0.2Te

Characteristics of photoluminescence (PL) originating from high-density exciton magnetic polarons (HD-EMPs) for Cd0.8Mn0.2Te were investigated. The PL appeared only under selective excitation of the localized excitons, and the intensity increased superlinearly with the excitation density. Directivity of the PL was revealed. Therefore, it is concluded that the superlinear increase in the PL intensity resulted from a light amplification process owing to the stimulated emission. In addition, the existence of birefringence that originates from a uniaxial gradation of the Mn ion concentrations was revealed. The degree of circular polarization (DOCP) of the PL is important to obtain the spin alignment state of the HD-EMPs. The initial DOCPs of the PL were examined by removing a variation of the polarization during propagation inside the sample. As a result, it was found that the initial DOCPs of the PL were almost constant for the photon energy. The obtained initial DOCPs exhibited different values for right- and left-circularly polarized excitations, which resulted from different mechanisms of the spin alignment of the HD-EMPs.