TEMPERATURE-DEPENDENCE OF THE MAGNETIC EXCITATION-SPECTRA OF YBA2CU2.9ZN0.1O6.75

Neutron scattering measurements of magnetic excitations in YBa2Cu2.9Zn0.1O6.75 (T(c) less-than-or-equal-to 10 K) have been performed. In contrast to the corresponding pure sample with the same oxygen number (T(c) congruent-to 66 K) where no peak of the antiferromagnetic correlation was detected for excitation energies below 15 meV, we have observed clear scattering contribution in the same energy range at all temperatures studied. A detailed study of chi''(omega) at (pi, pi) in this Zn-substituted sample suggests 1) an existence of the gap-like structure at high temperatures (100 K < T < 200 K) and 2) the enhancement of the spectral weight at low energies along with the loss of the itinerant nature of the electrons at low temperatures (T < 50 K).