Cu NQR Study on the “Wipeout” Phenomenon in YBa₂Cu₃O_y

Abstract

We have investigated if the wipeout phenomenon observed for the NQR signal of La_2-xSr_xCuO₄ in the region x∼ 1/8 at low temperatures, can also be observed in YBa₂Cu₃O_y system, and found no evidence in the 60 K plateau and higher carrier concentration regions of y. Only in the region of y<6.5, where at least part of hole carriers is localized, the reduction of Cu NQR spectra at low temperatures has been found. The inhomogeneous distribution of these localized carriers seems to cause the wipeout phenomenon. The wipeout phenomenon observed for YBa₂(Cu_0.98Zn_0.02)₃O_y in the wide region of y can also be understood by the same mechanism.