Combined EPR and ODMR study of Ce3+ optical emitters in yttrium aluminium garnet

Abstract

Electron paramagnetic resonance (EPR) was detected in the ground state of Ce3+ ions in YAG:Ce single crystals by monitoring the intensity of photoluminescence under nonresonant excitation. The photoluminescence intensity was found to increase strongly in magnetic field at liquid helium temperature. The optically detected magnetic resonance (ODMR) effect was of the order of percents and corresponded to resonance decrease in the luminescence intensity. ODMR correlated with the conventional EPR spectra of Ce3+ ions, which occupy the dodecahedral Y3+ sites in the YAG crystal lattice. The increase of the PL intensity in magnetic field was concluded to be caused by Boltzmann distribution between spin sublevels of the ground state of Ce3+ ions. The ODMR tend to equalize the populations of levels in resonance and results to a decrease of PL intensity. Different types of Ce3+ centres characterized by the presence of nearby antisite defects were observed, which should be taken into account in applications of single ion spectroscopy based applications of YAG:Ce.