Search for Orbital-Current Effects in Y$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$ using $^{89}$Y NMR

Recent efforts at explaining the exotic electronic properties of cuprates by involving orbital currents attracted a lot of attention. Here we present $^{89}$Y NMR measurements on an oriented $\mathrm{Y_{2}Ba_{4}Cu_{7}O_{15-\delta}}$ powder sample to search for the possible orbital-current phase. The temperature behavior of the $^{89}$Y line width and the spin-lattice relaxation rate in the normal-conducting phase were investigated in the normal-conducting state of the compound. The study provides upper limits for a static magnetic field and the amplitude of a fluctuating magnetic field at the Y site of $\alt 0.15mT$ and $\alt 0.7mT$, respectively. These values provide significant constraints on possible static or quasi-static orbital currents.