High-temperature spin relaxation process in Dy2Ti2O7 probed by 47Ti-NQR

We have performed nuclear quadrupole resonance (NQR) experiments on (47)Ti nuclei in Dy(2)Ti(2)O(7) in the temperature range of 70-300 K in order to investigate the dynamics of 4f electrons with strong Ising anisotropy. A significant change in the NQR frequency with temperature was attributed to the variation of the quadrupole moment of Dy 4f electrons. A quantitative account was given by the mean-field analysis of the quadrupole-quadrupole (Q-Q) interaction in the presence of the crystalline-electric-field splitting. The magnitude and the temperature dependence of the nuclear spin-lattice relaxation rate were analyzed, including both the spin-spin and the Q-Q interactions. The results indicate that these two types of interaction contribute almost equally to the fluctuation of Dy magnetic moments.