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Comment on ``Superconducting PrBa_2Cu_3O_x''

V. N. Narozhnyi·S. -L. Drechsler
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Abstract

Recently, Zou et al. (Phys. Rev. Lett. 80, 1074, 1998) reported the observation of bulk superconductivity (SC) for a PrBa_2Cu_3O_x (Pr123) single crystal grown by the traveling-solvent floating zone (TSFZ) method. The aim of this Comment is to show the inconsistency of the value of effective magnetic moment μ_{eff} reported by Zou et al. (2.92μ_B) with their magnetic susceptibility data. The estimation made directly from their data points gives a considerably smaller value of μ_{eff}=2.09μ_B. At the same time the values of mu_{eff}=2.9μ_B and 3.1μ_B were obtained for our Pr123 single crystals grown by flux method for H||ab-plane and H||c-axis, respectively. This suggests that Pr occupies only about a half of the RE sites in TSFZ crystal. The other half of the RE sites is occupied most probably by the nonmagnetic Ba. Noteworthy, SC with T_c=43 K was observed earlier for Pr_{0.5}Ca_{0.5}Ba_2Cu_3O_{7-y} thin films. Ba^{2+} has a larger ionic radius than Pr^{3+} and so the substitution of Ba for Pr could give a natural explanation not only for the SC in TSFZ Pr123 but also for the elongation of the distance between the CuO_2 planes observed by Zou et al.

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V. N. Narozhnyi, S. -L. Drechsler. 1998-11-18. Comment on ``Superconducting PrBa_2Cu_3O_x''. https://doi.org/10.1103/physrevlett.82.461

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