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 geometries. 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 1200 and 3000 cm(-1) (i.e. 150 and 375 meV). This modification of the line 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 well above the gap energy cannot be understood within models clarifying the origin of superconductivity-induced changes as the spin fluctuations seen by nuclear magnetic resonance (NMR) or neutron scattering. (C) 1997 Elsevier Science B.V.