Site Assignment for Copper NQR Lines in YBa₂Cu₃O_7−y

抄録

NQR spectra of Cu in both SmBa₂Cu₃O_7−y and GdBa₂Cu₃O_7−y were observed around 20–23 and 30–33 MHz, which are almost in the same range as those observed in YBa₂Cu₃O_7−y. Study of the relaxation process in Sm- and GdBa₂Cu₃O_7−y reveals a large increase in the nuclear relaxation rate, 1⁄T₁, for Cu at 32.5 MHz, while a small increase for Cu at 22.5 MHz. The difference in the enhancement of each line, which is governed by rare-earth spin fluctuations, enables us to definitely assign the signals at 32.5 MHz and 22.5 MHz to the planar and chain sites, respectively, based on a quantitative point of view.