Specific heat of a DyBa2Cu3O7-y single crystal in magnetic fields up to 8 T

The specific heat of a twinned DyBa2Cu3O7-y (DyBCO) single crystal has been measured in magnetic fields up to 8 T near T-c. The measurements were perf ormed on a small single crystal with an a.c. calorimetry technique. We have scaled the specific heat both by the method of removing a non-singular bac kground and by the method of scaling the magnetic field derivative of the s pecific heat. Both lowest Landau level (LLL) scaling and 3D XY scaling have been tested by these methods. We find that by the method of field derivati ve scaling, the two models give similar results, but by the method of remov ing a non-singular background, the LLL scaling fails in fields below 2 T. O n the low temperature side of the transition, small steps are observed in l ow fields which turn into small peaks (similar to 0.3% of C/T) for higher f ields. The position of these peaks is consistent with the vortex melting Li ne and gives a melting entropy of 0.3 K-B per vortex per CuO2 bi-layer in a n applied magnetic field of 5 T. (C) 1999 Elsevier Science B.V. All rights reserved.