Abstract
We present studies of the thermal, magnetic, and electrical transport properties of polycrystalline PrBa 2 Cu 4 O 8 prepared at ambient oxygen pressure. Measurements of the low-temperature specific heat C(T) and magnetic susceptibility χ(T) show similar results as in PrBa 2 Cu 3 O 7 . An anomaly observed at 17 K in C(T) and dχ/dT may be due to the antiferromagnetic ordering of the Pr sublattice. The upper limit of the entropy associated with the magnetic ordering is estimated to be 6.6 J/mol K. The free magnetic moment from a simple Curie-Weiss fit is 3.11μ B . These similarities in magnetic properties of PrBa 2 Cu 3 O 7 and PrBa 2 Cu 4 O 8 suggest that the magnetic coupling mechanism might be mainly associated with the CuO 2 planes. The resistivity p(T) is nearly metallic from 1.5 to 300 K. Comparisons of samples prepared by different methods suggest that the anomaly in resistivity around 200 K may be extrinsic. The behavior of p(T) is rather puzzling and cannot be explained simply by a dimensional crossover of charge transport arising from the double CuO chains. Other similarities and differences of the mentioned physical properties between PrBa 2 Cu 4 O 8 and PrBa 2 Cu 3 O 7 are stressed as well.