Extraordinary behaviour of the Y1−xPrxBa2Cu3O7−δ system

Investigations of Y1−xM x Ba2Cu3O7−δ (M=Ce, Th)c-axis oriented thin film specimens show that the rate of depression ofT c withx is larger for M=Th, than for M=Ce and Pr, and suggest that Ce, like Th, is tetravalent in this compound. Hall effect measurements on Y1−xPr x Ba2Cu3O7−δ single crystals reveal aT2 dependence of the cotangent of the Hall angle in the normal state and a “negative Hall anomaly” belowT c in the superconducting state, in agreement with recent reports. Our research shows that the depth, Δ, of the negative Hall signal scales withT/T c and that the maximum value of Δ decreases linearly withx and vanishes atx≈0.24. Magnetoresistance measurements on Y1−xPr x Ba2Cu3O7−δ single crystals indicate that the irreversibility lineH(T*) obeys a universal scaling relation characterized by anm=3/2 power law nearTc, with a crossover to a more rapid temperature dependence of belowT/T c ≈0.6, similar to that observed for polycrystalline specimens.