Raman scattering study of the geometrically frustrated pyrochlore Y2Ru2O7

Geometrically frustrated pyrochlore Y2Ru2O7, which shows a spin-glass-like transition at T-G similar to 80 K, were investigated by temperature-dependent Raman scattering. Three discernable phonons appear around 315, 410, and 510 cm(-1) without any abrupt change in the number of Raman active modes within the temperature range of 10-300 K. Fitting each phonon with Lorentz oscillators, we analyzed the effects of temperature on the phonon frequencies and the linewidths. The temperature-dependence of the mode near 510 cm(-1) shows abnormal behavior below T-G, while the other two phonons follow the usual thermal effect of lattice vibration. This behavior can be understood in terms of spin-phonon coupling. Considering the atomic modulations of each phonon mode, it is conjectured that the 510 cm(-1) phonon mode is isotropically coupled to the spin degree of freedom, while the other modes are not. (C) 2006 Elsevier B.V. All rights reserved.