ESR study of Mn2+ red emission in CaGa2S4 codoped with a REE

The ternary compound CaGa2S4 doped with Mn2+ exhibits a weak red emission, which can be enhanced by about ten times by co-doping with a rare earth element (REE). To clarify the mechanism of this enhancing effect, the site of the Mn2+ substitution is investigated through ESR measurements using a single crystal of CaGa2S4:Mn2+ (0.1 mol%). As a result, three sets of signals originating from different Mn sites were observed. Considering the angular dependences of the observed signals and the symmetry of the Ca and Ga sites, we can infer that Mn2+ ions occupy the Ca sites.