  The temperature and field dependences of the trapped magnetic fields and of
the frozen magnetoresistance of (Pb)Bi-Sr-Ca-Cu-O ceramics and Bi-based
magnetron films are investigated. It is found that in the resistive transition
region of granular Bi-HTSC the trapped magnetic fields become highly
inhomogeneous and alternating in sign at scale of less than 50 microns. Unlike
ceramic the films have critical temperature of trapping lower than the upper
temperature of magnetoresistance disappearance. The experimental results are
explained by a model in which the magnetic fields are trapped in
superconducting loops embedded in Josephson weak links medium. The loops nature
which is essentially different for films and ceramics is discussed. Observed
temperature and field dependences of trapped field are in good agreement with
those calculated for normal law of the loops distribution on critical fields.
