Electron spin dynamics of Ce${}^{3+}$ ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

Abstract

The spin relaxation dynamics of 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 4$f$ ground state, while pump-probe Faraday rotation provides also access to the excited 5$d$ state. We measure a millisecond spin-lattice relaxation time $T_1$, a microsecond spin coherence time $T_2$ and a $\sim 10$ ns inhomogeneous spin dephasing time $T_2^{\ast }$ for the Ce${}^{3+}$ ground state at low temperatures. The spin-lattice relaxation of Ce${}^{3+}$ ions is due to modified Raman processes involving the optical phonon mode at 125 cm${}^{-1}$. The relaxation at higher temperature goes through a first excited level of the ${}^2$F${}_{5/2}$ term at about $\hslash \ddot{I}‰\approx 228$ cm${}^{-1}$. Effects provided by the hyperfine interaction of the Ce${}^{3+}$ with the ${}^{27}$Al nuclei are observed.

10 pages, 13 figures