Negative Magnetoresistance in Granular Bi - HTSC with Trapped Magnetic   Fields
  Magnetoresistive properties of granular Bi-based HTSC with trapped magnetic fields are investigated in the temperature region near superconducting transition . The effect of trapped field and transport current values and orientations on the field dependence of magnetoresistance is studied. It is found that for the magnetic field parallel and the current perpendicular to trapping inducing field the field dependence of magnetoresistance is nonmonotonic and magnetoresistance turns out to be negative for small fields. The magnetoresistance sign inversion field increases roughly linear with the trapped magnetic field and slightly decrease with transport current. The results are explained in the framework of model of magnetic flux trapping in granules or superconducting loops embedded in weak links matrix. 
A. A. Sukhanov, V. I. Omelchenko