Hall effect in the mixed stat detwinned single crystals

Abstract

We have measured the Hall and longitudinal resistivities of detwinned (Formula presented)(Formula presented)(Formula presented)(Formula presented)(Formula presented) single crystals with x=0.05, 0.10, 0.15, and 0.20. In the mixed state, the samples with x=0.05 and 0.10 exhibit a sign reversal of the Hall resistivity. However, the sign reversal is absent in the samples with x=0.15 and 0.20. The disappearance of the sign reversal in the x=0.15 sample represents a new finding. It indicates that the presence or absence of the sign reversal is not a thermal effect, since this sample has a (Formula presented) of 82 K, and many other superconductors with the same (Formula presented) exhibit the sign reversal. We have calculated the in-plane Hall conductivity, and find that it can be expressed as the sum of two terms, (Formula presented)/H and (Formula presented)H. (Formula presented) and (Formula presented) are independent of field, but depend on temperature and Pr concentration. The temperature dependences of (Formula presented) and (Formula presented) weaken with increasing Pr concentration up to the disappearance of the sign reversal, at which point (Formula presented) changes sign and begins to depend more strongly on temperature again. © 1996 The American Physical Society.