Photo-induced magnetization and polarized photoluminescence of CdMnTe under high-density excitation of localized excitons

Photoluminescence (PL) originating from high-density exciton magnetic polarons (HD-EMPs) was reported for Cd0.8Mn0.2Te. In the present study, we measured the polarization of the PL for circularly polarized excitation light. PL components with circular polarization were observed, indicating the presence of a spin-aligned state for the HD-EMPs despite the absence of an external magnetic field. By comparing the degree of circular polarization (DOCP) of the PL for the excitation light with that of the opposite circular polarization, we concluded that two generation mechanisms were responsible for the spin-aligned state of the HD-EMPs. In the first mechanism, the spin alignment of the HD-EMPs was determined by the spins of photoexcited electrons (holes). In the other mechanism, the spin state of the HD-EMPs was determined spontaneously along a certain axis according to interactions with Mn ions. Moreover, we measured the time-resolved photo-induced Faraday rotation under circularly polarized pump light. Our findings support the existence of the aforementioned two generation mechanisms for the spin-aligned HD-EMPs. The results presented in this paper are significant for the study of the macroscopic behavior of correlated high-density exciton systems.