NEUTRON-IRRADIATION EFFECTS ON THE V-I CHARACTERISTICS OF YBA2CU3O7-DELTA TWINNED CRYSTALS - LINKING TRANSPORT RESULTS IN A VARIETY OF COPPER-OXIDE SUPERCONDUCTORS

We have investigated the depinning process of magnetic flux vortices i n twinned crystals of YBa2Cu3O7-delta in intermediate applied magnetic fields parallel to the crystallographic c axis through precise resist ivity measurements before and after fast-neutron irradiation. Of parti cular interest for each field is the power-law dependence of the elect ric field on current density, E proportional to J(n), at a well define d temperature which separates a nonlinear region below from a more lin ear, dissipative region above. We find that n shows a striking depende nce on the estimated value of the Larkin-Ovchinnikov length. The relat ion is not only manifest before and after irradiation but also for a v ariety of samples, including films, crystals, and at least two copper oxides other than YBa2Cu3O7-delta.