MAGNETIC-PROPERTIES, SPECIFIC-HEAT STUDIES AND MOSSBAUER MEASUREMENTSOF PRBA2NBCU2O8

PrBa2NbCu2O8 has been studied by DC susceptibility and specific heat m easurements to determine the magnetic behavior of the Pr sublattice, a nd by a 1% Fe-57-doped sample to determine the magnetic behavior of th e Cu (2) sites. The Pr sublattice and the CuO2 planes are both antifer romagnetically ordered at 11.6 and 360 K, respectively. The Pr contrib ution to the specific heat DELTAC(p)(T) was calculated by subtracting the data of LaBa2NbCu2O8 as background. The entropy associated with th e magnetic transition is 6.7 J/mol K, intermediate between the expecte d values for Pr4+ and Pr3+. At low temperatures the magnetic contribut ion has the form of DELTAC(p)(T) = MT3.1 characteristic of 3D antiferr omagnetic magnons. In contrast to PrBa2Cu3Oz, no linear term for the e lectronic specific heat is observed in PrBa2NbCu2O8.