Temperature Dependence of the Magnetic Excitation Spectra of YBa2CU2.9Zn0.1O6.75

Neutron scattering measurements of magnetic excitations in YBa2Cu2.9Zno.1O6.75 (7”c< 10 K) have been performed. In contrast to the corresponding pure sample with the same oxygen number (Tc - 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 x”(co) at (tt, 7t) in this Zn-substituted sample suggests 1) an existence of the gap-like structure at high temperatures (100 K < r< 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 (r<50 K).