Sign reversal of the Hall effect in YBa2(Cu1-x)3O7-δ single crystals

Abstract

We have measured the in-plane Hall effect and in-plane resistivity of cobalt-doped YBa2Cu3O7-δ (YBCO) single-crystal samples. The concentration of cobalt ranged from 1 to 3%. As the applied field was varied, a sign reversal of the Hall resistivity was seen for 1 and 2% Co-doped samples, but not for the 3% sample. Our results are expressed in terms of conductivities, as recently recommended by the work of Dorsey et al. and Kopnin et al. In the mixed state just below the superconducting transition temperature Tc, the Hall conductivity σxy is the sum of two terms, C1/H and C2H, where C1 and C2 are field-independent but temperature-dependent. As previously observed by Ginsberg and Manson for undoped YBCO, the coefficient C1 is approximately proportional to τ2 and C2 is approximately linear in τ, where τ = 1-(T/Tc). The values of C1 and C2 are presented for each cobalt concentration. © 1995 Plenum Publishing Corporation.