Abstract

The effect of praseodymium doping on the transverse electrical resistance of Y1−yPryBa2Cu3O7−δ single crystals is investigated by electrical resistance measurements. The resistance curves can be fitted well to an expression accounting for the thermo-activated variable-range hopping charge transfer in conjunction with the fluctuation conductivity in the 3D Aslamazov–Larkin model. Our analysis of the Pr concentration dependence of the fitting parameters shows that in the concentration range 0.34<y<0.43 the sample is breaking up into separate conducting regions (granules) and the conductivity acquires a character peculiar to the variable-range hopping mechanism. With increasing Pr concentration the contribution of electron scattering on impurities monotonically increases, while the region of superconducting fluctuations shrinks away. A pronounced anisotropy of the coherence length has been observed, revealing the Cooper pairs size in the direction across the layers to be two orders of magnitude smaller than its in-plane value.

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