Electron spin dynamics ofCe3+ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

The spin relaxation dynamics of ${\mathrm{Ce}}^{3+}$ ions in heavily cerium-doped YAG crystals is studied using pulse-electron paramagnetic resonance and time-resolved pump-probe Faraday rotation. Both techniques address the $4f$ ground state, while pump-probe Faraday rotation also provides access to the excited $5d$ state. We measure a millisecond spin-lattice relaxation time ${T}_{1}$, a microsecond spin coherence time ${T}_{2}$, and a $\ensuremath{\sim}10$ ns inhomogeneous spin dephasing time ${T}_{2}^{*}$ for the ${\mathrm{Ce}}^{3+}$ ground state at low temperatures. The spin-lattice relaxation of ${\mathrm{Ce}}^{3+}$ ions is due to modified Raman processes involving the optical phonon mode at $\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}125\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. The relaxation at higher temperature goes through a first excited level of the $^{2}\mathrm{F}_{\frac{5}{2}}$ term at about $\ensuremath{\hbar}\ensuremath{\omega}\ensuremath{\approx}228\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. Effects provided by the hyperfine interaction of the ${\mathrm{Ce}}^{3+}$ with the $^{27}\mathrm{Al}$ nuclei are observed.