HIGH FREQUENCY MODES OF YBa2Cu3O6+δ AND ITS VARLATIONS WITH OXYGEN CONTENT

Inelastic neutron scattering spectra of YBa2Cu3O6+δ sample with several different oxygen contents δ have been obtained in the energy range from 10 to 150 meV at a new wide angle (～30°) Be-filter detecter spectrometer, CIAE,Beijing. The experiments show that :(l)For samples with δ=0 and δ=0.2, some strong high frequency modes appear in the energy range from ～60 to ～150 meV,and the intensity of modes does not decrease as the temperature is above Neel point until 466K. For samples with δ=0.78 and 0.97, however, the high frequency modes are not present and the scattering intensity spetra in the energe range from 70 to 150 meV seem to be a featureless background. (2)In the measured energe range from 10 to 150 meV the scattering intensities of sample with δ=0 and 0.2 is about two to three times as that of sample with δ = 0.78 and 0.97. (3) In the energe range below 60 meV, there are many distinct scattering peaks which are almost not shifted with δ, most of peaks are in a-greement with results of Renker and Parshin, and other peaks are observed for the first time. The strong dependence of high frequency modes and scattering intensities on the oxygen content δ would attribute to antiferromagnetics spin wave excitation.