Magnetic ordering and transport properties ofPrBa2Cu4O8

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 (T) show similar results as in PrBa 2 Cu 3 O 7 . An anomaly observed at 17 K in C(T) and d/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 3.11 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 (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 (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.

Thermodynamic properties of superconducting and non-superconducting Pr2Ba4Cu7O15-δ compounds with metallic double chains

“…These values are almost consistent with the effective moment of Pr124 (µ eff = 3.11µ B ). 6 In particular, the µ eff of the superconducting sample is close to that of Pr 3+ (3.54 µ B ). The magnetoresistance of the as-sintered and 48-hreduced samples also differ at high temperatures (above T on c = 26.5 K).…”

“…The C/T of the non-superconducting as-sintered sample exhibits a λ− like enhancement associated with the antiferromagnetic transition of Pr ions, as previously reported in non-superconducting Pr123 and Pr124 systems. 6,18 As the external magnetic field in- creases, this sharp increase is suppressed and peaks at lower temperatures. At 9 T, the thermodynamic peak is considerably depressed and is located around 15 K. At low temperatures (below 5 K), the specific heat also exhibits a strong field dependence, for reasons which have not yet been clarified.…”

“…In the as-sintered sample, a typical anomaly in χ occurs near 17 K. This anomaly is associated with an antiferromagnetic transition of the Pr sublattice, as previously reported in Pr123 and Pr124 systems. 5,6 On the contrary, the 48-h-reduced sample becomes superconductive below T on c = 26.5 K. The superconducting volume fraction f was estimated from the magnetic data taken at 10 mT by f = χ · ρ/4π × 100, where χ and ρ denote the magnetic susceptibility per unit weight and the sample density (5.3 g/cm 3 ), respectively. As displayed in the inset of Fig.2 (b), the volume fraction reaches ∼30 % at 4 K, indicating bulk superconductivity.…”

“…4 The carrier concentration of doped double chains of Pr124 is difficult to vary, because it is thermally stable up to high temperatures. In addition, Pr ions in both Pr123 and Pr124 become antiferromagnetic ordered at the antiferromagnetic transition temperature T N = 17 K. 5,6 The compound Pr 2 Ba 4 Cu 7 O 15−δ (Pr247) is an intermediate between Pr123 and Pr124. In this compound, CuO single-chain and double-chain blocks are alternately stacked along the c-axis 7,8 (see Fig.1).…”

Dimensionality-driven spin-flop transition in quasi-one-dimensionalPrBa2Cu4O8

“…1). [5][6][7] Due to strong hybridization of the 2p-orbitals of oxygen with the Pr 4f -orbitals, 8 the CuO 2 plane carriers localize and order antiferromagnetically around T N (Cu) ∼ 220 K. 9 The Pr cations also order antiferromagnetically at T N (Pr) = 17 K, 10 a temperature that is one order of magnitude higher than the T N values found in all the other rare-earth element containing layered cuprates.…”