RAMAN-SCATTERING OF MAGNETIC EXCITATIONS IN Y1-XPRXBA2CU3-YALYO7-DELTA SINGLE-CRYSTALS

Magnetic excitations and their role for the superconductivity in cupra te superconductors have been widely discussed in the literature. Here, we present a study of Y1-xPrxBa2Cu3-yAlyO7-delta single crystals usin g Raman spectroscopy in an energy range of 50 - 10000 cm(-1) Raman shi ft. The high energy range is dominated by a two-magnon scattering proc ess at 3J, where J is the superexchange energy. In the Pr-123 single c rystal, we find J = 720 cm(-1), a damping of the one-magnon states Gam ma = 200 cm(-1), and a resonance energy of 2.79 eV for the two-magnon excitation. The two-magnon peak shows a continuous increase of the one -magnon damping with decreasing x and a nearly constant J across the p hase transition to the superconductor. Especially, we find a weak two- magnon peak for a superconductor with a T-c = 86 K.