The Effect of Anisotropy in Hc2 on the Breadth of the Resistive Transition of Polycrystalline YBa2Cu3O7−x in a Magnetic Field
Previous studies have shown that an applied magnetic field severely broadens the transition to the superconducting state in polycrystalline YBa2Cu3O7−x and La2CuO4-based superconductors. Two possible sources of this broadening are the poor superconducting properties of the intergranular material in these granular superconductors and the anisotropy in the upper critical field Hc2 arising from the layered nature of their crystal structures. Both factors can cause low values of the critical current density in magnetic fields for polycrystals, but whereas the effect of granularity can in principle be removed by proper processing, the effect of anisotropy is intrinsic and can severely limit the usefulness of randomly oriented polycrystals if the anisotropy is large enough.
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