The effect of a constant magnetic field to 12.7kOe on the temperature dependences of the electric conductivity of aluminum-doped YBaCuO single crystals with a system of unidirectional twinning boundaries was investigated. The temperature dependences of the excess paraconductivity and the field dependence of the coherence length ξc(0,H) along the c axis were determined in the basal ab plane. It was determined that the twinning boundaries were effective centers of scattering of fluctuation carriers. The temperature dependences of the excess paraconductivity were interpreted on the basis of the Hikami-Larkin theoretical model of fluctuation conductivity for layered superconducting systems. The reasons for the suppression of three-dimensional superconducting fluctuations and the non-monotonic dependence of ξc(0,H) in weak magnetic fields with the magnetic field vector oriented along the c axis were considered.

Magnetoresistance and 2D-3D Crossover in Aluminum-Doped YBa2Cu3−zAlzO7−δ Single Crystals with a System of Unidirectional Twinning Boundaries. A.A.Zavgorodniĭ, R.V.Vovk, M.A.Obolenskiĭ, A.V.Samoĭlov: Low Temperature Physics, 2010, 36, 115-8