Lack of evidence for orbital-current effects in the high-temperature Y2Ba4Cu7O15-delta superconductor using 89Y nuclear magnetic resonance.

We have performed NMR measurements at the Y site on a c-axis-oriented powder sample of the cuprate superconductor Y2Ba4Cu7O15-delta to search for the possible orbital-current phase. The temperature dependence of the Y linewidth and relaxation behavior in the normal-conducting phase were studied down to 100 K. These measurements give upper limits for a static magnetic field and the amplitude of a fluctuating magnetic field at the Y site of < or approximately 0.15 and < or approximately 0.7 mT, respectively. These values provide significant constraints on possible static or quasistatic orbital currents.