Fluctuation conductivity and pseudogap in HoBa2Cu3O7-δ single crystals under pressure with transport current flowing under an angle 45° to the twin boundaries

The influence of hydrostatic pressure up to 0.48 GPa on the fluctuation conductivity sigma'(T) and pseudogap (PG) Delta(*)(T) of slightly doped HoBa2Cu3O7-delta single crystals with T-c approximate to 62 K and delta approximate to 0.35 is studied with current passing under an angle 45 degrees to the twin boundaries. It is shown that near T-c the conductivity sigma'(T) is well described by the Aslamasov-Larkin and Hikami- Larkin fluctuation theories demonstrating 3D-2D crossover with the increase of temperature. Delta(*)(T) displays two representative maxima at T-max1 approximate to 219 K and T-max2 approximate to 241 K likely caused by the phase stratification of the single crystal. Pressure leads to disappearance of these maxima and linear Delta(*)(T) with a positive gradient at high temperatures. Essentially, with the removal of pressure the maxima are restored. The comparison of our results with those obtained for YBa2Cu3O7-delta d sheds more light on the role of magnetic subsystem in the high-T-c superconductors. (C) 2014 Elsevier B.V. All rights reserved.