SPECIFIC-HEAT OF PURE Y1-XPRXBA2CU3O7-DELTA SINGLE-CRYSTALS IN MAGNETIC-FIELDS

Specific heat measurements have been performed on single crystals of Y 1-xPrxBa2Cu3O1-delta (x=0.33, 1) in the temperature range 2 K<T<50 K w ith magnetic fields up to 7.5 T, both parallel and perpendicular to th e c-axis. The crystals were grown in BaZrO3 crucibles and therefore th e possibility of crucible contamination in the crystals is reduced to a large extent. A large linear term with gamma=207 mJ/mol K-2 was dete rmined for x=1 and the crystal field contribution due to Pr ion was ca lculated for both the samples. The transitions were found to be sharp lambda type for x=1 with the ordering temperature at 16.6 K and very b road for x=0.33 with the transition temperature below 2 K. Also, the t ransition temperatures increased for x=0.33 and decreased for x=1 with increasing magnetic fields indicating a different type of interaction for these two samples. The coupling in the ab plane was found to be s tronger than in the c-axis. (C) 1997 American Institute of Physics.