Magnetic ordering and superconductivity inY1−xPr

X-ray absorption spectroscopy of detwinnedPrxY1−

“…͑ii͒ Alternatively, a magnetic pair-breaking effect by the local moment of the Pr atom has been invoked as an explanation, 12,27 since the degradation of T c with increasing Pr concentration seemed to be compatible with AbrikosovGorkov theory. However, pair breaking itself does not localize charge carriers and, thus, explains neither the nonmetallicity in PrBa 2 Cu 3 O 7 nor the recovery of superconductivity upon doping with Ca.…”

“…Among those rare-earth-based cuprates that are isostructural to YBa 2 Cu 3 O 7Ϫy , the PrBa 2 Cu 3 O 7Ϫy compound is a puzzling exception since it shows neither metallic nor superconducting behavior. [6][7][8][9][10] Upon substituting Pr into the Pr x Y 1Ϫx Ba 2 Cu 3 O 7Ϫy system, T c decreases [11][12][13] and, in the case of yϷ0.1, finally vanishes for Pr fractions x beyond 0.55. This transition seems to be accompanied by a change from metallic to semiconducting characteristics.…”

“…This transition seems to be accompanied by a change from metallic to semiconducting characteristics. 10,12,14 Concurrently, an antiferromagnetic order of the copper atoms in the planes [15][16][17][18] and of the Pr atoms between the planes 15,16,18 sets in, resulting in Néel temperatures T N,Cu (2) Ϸ285 K and T N,Pr Ϸ 17 K for the fully Pr-substituted compound ͑xϭ1͒. Since PrBa 2 Cu 3 O 7Ϫy has all the structural features that are considered essential for high-temperature superconductivity in YBa 2 Cu 3 O 7Ϫy , such as CuO 2 planes and CuO 3 chains which lead to a doping of the planes, differences in the electronic structure and in the hole distribution between these structural units may reveal key parameters for hightemperature superconductivity in RBa 2 Cu 3 O 7Ϫy and, therefore, might help to close in on the mechanism that underlies superconductivity.…”

“…This approach implies that the suppression of superconductivity results from a reduced number of charge carriers in the CuO 2 planes. Magnetic susceptibility, 6,8,12 Hall effect, 8 thermopower, 7,9,10 nuclear magnetic resonance, 15 muon-spin relaxation, 16 and neutron diffraction measurements [22][23][24] have been interpreted in terms of hole depletion. On closer inspection, however, it has been shown that these results can also be understood as an indication for Pr 3ϩ .…”

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

“…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.…”