NQR study of copper in Lu[sub 0. 9]Pr[sub 0. 1]Ba[sub 2]Cu[sub 3]O[sub 7]

Nuclear quadrupole resonance (NQR) of copper in Lu[sub 0.9]Pr[sub 0.1]Ba[sub 2]Cu[sub 3]O[sub 7] at 4.2 K has been observed. The resonances of [sup 63]Cu(II) and [sup 65]Cu(II) have been observed at 31.50 and 29.15 MHz, respectively. These frequencies are the same as those in YBa[sub 2]Cu[sub 3]O[sub 7] but not in accordance with the expectations from the decrease of resonance frequency in [ital R]Ba[sub 2]Cu[sub 3]O[sub 7] compounds. [nu][sub [ital Q]][sup 63]/[nu][sub [ital Q]][sup 65] is 1.08 which is the ratio of the [ital eQ]([sup 63]Cu)/[ital eQ]([sup 65]Cu), implying that there is no static magnetic field at the Cu(II) site. The relaxation times [ital T][sub 1] and [ital T][sub 2] at 31.50 MHz have been determined and are found to be 42 ms and 140 [mu]s, respectively. [ital T][sub 1] is much less than that ([similar to]1 s) in YBa[sub 2]Cu[sub 3]O[sub 7] and EuBa[sub 2]Cu[sub 3]O[sub 7], indicating that fluctuating moments are present in the material. These could be either on Cu ions that are close to Pr ions or on Pr ions themselves. The contrasting behavior of resonance frequency and [ital T][sub 1] in Lu[sub 0.9]Pr[sub 0.1]Ba[sub 2]Cu[sub 3]O[sub 7] with respect to other 1:2:3 compounds is commented upon.