TEMPERATURE-DEPENDENT LIFETIME OF SPIN EXCITATIONS IN EUBA2CU3O6,YBA2CU3O6

We have measured the light scattering by spin-pair excitations in single crystals of RBa2Cu3O6 (R=Y,Eu) for several polarization directions in the temperature range of 10 to 700 K. A strong broadening of the B1g and an enhancement of the A1g component is observed with increasing temperature. For all temperatures agreement between calculations and experimental light-scattering data has been obtained with J=810 cm-1 and a zone-edge spin-excitation damping which changes from 184 50 cm-1 (T=10 K) to 913 100 cm-1 (T=600 K). We conjecture that spin-lattice interaction significantly decreases the spin-excitation lifetime. © 1990 The American Physical Society.