Nuclear magnetic resonance study of the relaxation mechanisms of the 9Be, 27Al, and 29Si nuclei in Cr3+-doped Be3Al2Si6O18 crystals

The variations with temperature of the relaxation mechanisms of the 9Be, 27Al, and 29Si nuclei in emerald (Be3Al2Si6O18:Cr3+) single crystals were investigated by using a pulse NMR spectrometer. The values of the spin-lattice relaxation rates T1−1 for the three nuclei are different, and these differences are attributed to the differences between their Larmor frequencies and their local nuclear environments. The relaxation rates of the 9Be and 27Al nuclei undergo no abrupt changes within the temperature range 180-400 K, which indicates that there are no phase transitions within this temperature range. The spin-lattice relaxation rates of 9Be and 27Al were found to be proportional to temperature. Therefore, the nuclear spin-lattice relaxation processes of these two nuclei proceed via single-phonon processes.