Electron paramagnetic resonance and luminescent properties of Mn2+:MgGa2O4 phosphor

Electron-paramagnetic-resonance EPR and photoluminescence PL studies on magnesium gallate $(MgGa_{2}O_{4})$ phosphor activated with divalent manganese have been carried out. The EPR spectrum exhibits a six-line hyperfine structure centered at g=1.995, which is a characteristic of a $Mn^{2+}$ ion with a nuclear spin I=5/2. The spin-Hamiltonian parameters have been evaluated. The concentration and temperature 123-433 K dependences of EPR signals have been studied. The number of spins participating in resonance N with temperature obeys the Boltzman law and from the graph of log N versus 1/T the activation energy has been evaluated. The paramagnetic susceptibilities have been calculated from the EPR data at different temperatures and it is interesting to note that it obeys the Curie-Weiss behavior. The Curie constant has been evaluated from the 1/\chi versus T graph. A bright green photoluminescence according to the transition $ ^{4}T_{1} -> ^{6}A_{1}$ whose emission peak is located at 502 nm is observed from the phosphor under UV excitation when excited by 267-nm light. Such a stable luminescence performance is promising for use in the field of flat panel light-emitting devices. The mechanism involved in the generation of green emission has been explained in detail.