NQR Study of Copper in SmBa₂Cu₃O_7-<i>y</i>

Abstract

An NQR study of Cu in SmBa 2 Cu 3 O 7- y has been performed. Two pairs of signals were observed around 20-23 and 30-33 MHz. The nuclear spin lattice relaxation rate, T -1 1 at the higher frequency site shows a weak temperature dependence in the normal state, while it decreases rapidly without enhancement just below T c . The values of T -1 1 above 80 K are almost the same as that in Y-based compounds. At low temperatures, T -1 1 is governed by Sm spin fluctuations. From the analysis of this contribution, we conclude that the signals apearing around 30 and 22 MHz in Sm- and Y-based compounds are attributed to Cu in the Cu-O plane and Cu-O chain, respectively.