Cu(1)-nuclear quadrupole resonance in REBa₂Cu₃O₆ (RE=Rare earth)

Abstract

We have measured ^63,65Cu(1)-nuclear quadrupole resonance as a function of temperature in a number of REBa₂Cu₃O₆ materials with RE=rare earth atoms such as Nd, Sm, Eu, Gd, Dy, Ho, Er and Y. The results are discussed in the light of the fact that the major contribution to the Cu(1)-nuclear relaxation rate arises due to the fluctuation of the RE-spins. In the superconducting O₇-systems, formation of Cooper pairs, below T_c, modifies the fluctuation spectrum of the RE-spins. On the other hand, in the insulating O₆-materials, there is no such effect. The fluctuation spectrum of the RE spins, and therefore, the nuclear relaxation rate, in O₆-materials remains essentially unchanged in the investigated interval of temperature.