Magnetic ordering and transport properties

We present studies of the thermal, magnetic, and electrical transport properties of polycrystalline (Formula presented) prepared at ambient oxygen pressure. Measurements of the low-temperature specific heat (Formula presented) and magnetic susceptibility (Formula presented) show similar results as in (Formula presented) An anomaly observed at 17 K in (Formula presented) and (Formula presented) 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 (Formula presented) These similarities in magnetic properties of (Formula presented) and (Formula presented) suggest that the magnetic coupling mechanism might be mainly associated with the (Formula presented) planes. The resistivity (Formula presented) 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 (Formula presented) 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 (Formula presented) and (Formula presented) are stressed as well.