Room-temperature electron spin dynamics of Ce3+ ions in a YAG crystal

Circularly polarized optical excitation generates electron spin polarization in the lowest 5d state of rare-earth Ce3+ ions in a YAG crystal. The 5d electron spin dynamics is investigated in transverse and longitudinal magnetic fields by time-resolved pump-probe Faraday rotation. Long lived electron spin coherence with a dephasing time of 2.5 ns is found at room temperature. In a transverse magnetic field of 1 T, the electron spin coherence shows a distinct beating-like amplitude modulation due to several slightly different Larmor frequencies corresponding to different electron g factors of magnetically inequivalent positions of the Ce3+ ions in the crystal lattice. Hyperfine coupling between the 5d electron of Ce3+ ions and environmental nuclear spins dominates the spin relaxation, which can be efficiently suppressed by a longitudinal magnetic field as small as 10 mT. The dependence of electron spin relaxation on both the transverse and longitudinal magnetic fields agrees well with the one predicted theo...