Effect of Pr Doping on Transport Properties of Nd(Ba_2-xPr_x)Cu₃O_7+δ

Abstract

Solid-state-reacted polycrystalline Nd(Ba2-xPrx)Cu3O7+δ materials have been prepared and investigated using X-ray diffraction and resistivity measurements. Our results show that Nd(Ba2-xPrx)Cu3O7+δ is a superconductor when x<0.3. The Tc depression in superconductivity of Pr at Ba sites is due to both hole filling/localization and depairing effects. The normal state conductivity undergoes a dimensional crossover from two-dimensional to three-dimensional in the frame of the variable range hopping regime. The localization length of carriers shows that Pr doping localizes carriers in the normal state and causes the Tc depression. The magnetoresistance of the samples has been investigated within the thermally activated flux creep (TAFC) and Ambegaokar and Halperin (AH) phase slip models. The pinning energy and critical current density decrease with the applied magnetic field and Pr doping. A scaling relation as a power-law dependence of pinning energy on the magnetic field has been obtained. The derived pinning energy shows that Pr doping plays the role of a weak link.

Structural aspects and the conduction mechanism of Ln(Ba2–xPrx)Cu3O7+δ (Ln = Tm, Lu)

“…(2) Represents the effect of the magnetic moment of the impurity ion on pair breaking. As our results and other reports on similar samples [37,38] indicate, Pr at Ba sites has a marginal pair-breaking effect on superconductivity. On the other hand, the results for Y 1-x Pr x Ba 2 Cu 3 O y samples [37] show the fitting equation of T c = 92.3 -105.9x…”

“…This is expected because of the nonisovalent substitution of Pr 3+ -with the extended wavefunction -at Ba 2+ sites. The hole-filling/localization effect of Pr at Ba sites is strongly supported by the experimental results of Y(Ba 2-x Pr x )Cu 3 O y [37] and Nd(Ba 2-x Pr x ) Cu 3 O 7 [38].…”