INVESTIGATION OF THE TEMPERATURE, RESONANCE, AND SYMMETRY PROPERTIES OF THE SPIN-FLUCTUATION INTENSITY OF Y0.8PR0.2BA2CU3O7 USING RAMAN-SPECTROSCOPY

We present Raman spectra of high-energy spin excitations of a Y(0.8)Pr (0.2)Ba(2)Cn(3)O(7) thin film. At 300 K the line shapes above 600 cm(- 1) display a flat and structureless background in all scattering geome tries. Below 200 K, weak structures develop in A(1g) and B-1g symmetry that are significantly modified at T-c in the energy range between 12 00 and 3000 cm(-1) (i.e. 150 and 375 meV). This modification of the li ne shapes becomes resonant towards higher energies around 2.65 eV. No corresponding changes of the weak signal in the B-2g configuration was observed. The change of spin-fluctuation intensity at high energies w ell above the gap energy cannot be understood within models clarifying the origin of superconductivity-induced changes as the spin fluctuati ons seen by nuclear magnetic resonance (NMR) or neutron scattering. (C ) 1997 Elsevier Science B.V.