Temperature Dependence of the Magnetic Excitation Spectra of YBa₂Cu_2.9Zn_0.1O_6.75

Abstract

Neutron scattering measurements of magnetic excitations in YBa₂Cu_2.9Zn_0.1O_6.75 (T_c≤10 K) have been performed. In contrast to the corresponding pure sample with the same oxygen number (T_c\simeq66 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 χ″(ω) at (π, π) 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).