ANOMALOUS PEAKS IN THE THERMOPOWER OF SINGLE-CRYSTAL YBA2CU3O1-X

We present results for the thermopower of two ‘single’ crystals of YBa2Cu3O1−X from the transition temperature to 110K. The crystals were of variable ‘quality’ with Tc’s ranging from 73K to 92K. One of the crystals had three distinct domains with Tc’s of 73K, 81K and 90K as observed using ac susceptibility measurements. Although the thermopowers were qualitatively similar, they showed anomalous peaks in the vicinity of Tc. We have argued that the peaks are due to fluctuation effects, but the signature of the peaks, characteristic of a particular crystal, is the result of inhomogeneity, and suggests that the crystals are made up of a small number of domains with distinct Tc’s. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.