Glassy spin freezing and NMR wipeout effect in the high-T-c superconductorLa1.90Sr0.10CuO4: Critical discussion of the role of stripes - art. no. 144508

We report on La-139 and Cu-63 NMR/NQR measurements in the high-T-c supercon ductor La1.90Sr0.10CuO4, with T-c=26.5 K. Spin fluctuations probed by La-13 9 spin-lattice relaxation (T-1) continuously slow down on cooling through T -c. We argue that spin freezing and superconductivity are bulk effects in t his sample. Thus both phenomena have to coexist microscopically. The distri bution of La-139 T-1 values at low temperature reveals a wide spread of spi n fluctuation frequencies in CuO2 planes. A simple estimate shows that Cu-6 3 nuclei at sites where electronic fluctuations are the slowest are not obs ervable (wipeout effect) because relaxation times are too short. This means that the Cu-63 NQR wipeout, observed in this sample, can be explained prim arily by slow magnetic, rather than charge, fluctuations. The magnetic orig in of the wipeout is still compatible with a connection between wipeout and charge order [as proposed by Hunt et al., Phys. Rev. Lett. 82, 4300 (1999) ], but this connection is indirect. On the other hand, since the wipeout fr action is not an intensive quantity it cannot define a proper order paramet er and cannot be used by itself as a criterion for the existence of a strip e phase.