In-plane anisotropy and possible chain contribution to magnetoconductivity in YBa2Cu3O

The magnetoresistivity of untwinned YBa2Cu3O7-δ single crystals was measured in magnetic fields up to 12 T, for B parallel c and B parallel ab, at temperatures up to Tc+84K and Tc+50K, respectively. Two issues were addressed; determination of the in-plane coherence length anisotropy γ=ξb/ξa and discussion of the role of the CuO chains in the magnetoconductivity Δσ. A fluctuation conductivity theory that allows for an in-plane coherence length anisotropy (ξa≠ξb), as well as an extension of the usual Aronov-Hikami-Larkin theory that does not, were used in analyses. The results suggest that the anisotropy γ is close to 1. The analyses also suggest a contribution to the magnetoconductivity from the CuO chains of a sign which depends on the direction between field and current