The effect of mechanical loading on superconducting parameters of grains and Josephson junctions in YBa2Cu3O7–<i>δ</i> ceramics

The variation of the real component of the dynamic magnetic susceptibility χ′ in the superconducting ceramic YBa2Cu3O7–δ is investigated under (uniaxial) loading σ ≲ 0.1 GPa in the superconducting transition region. The existence of two regions within the superconducting transition width is established for the first time. These regions differ in the nature of the effect of stress on the parameters in the granulated superconductor in that the derivative dχ′/dσ is determined by the change in the intragranular diamagnetic properties just after the onset of the transition (88.5 &amp;lt; T &amp;lt; 90 K), and by a change in the properties of Josephson junctions between grains at lower temperatures (T &amp;lt; 87.5 K). A new effect, viz., a nonmonotonic hysteresis of the derivative dχ′/dσ in a magnetic field is observed. The observed regularities are attributed to a change in the Josephson currents in the network of weak links under mechanical stresses, and empirical estimates are obtained for the parameters determining the effect of mechanical loading on the properties of Josephson junctions in a ceramic. It is found that the diamagnetic properties of the ceramic are stable to temperature and load cycling.

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