A NEW-TYPE OF NONMONOTONIC FIELD-DEPENDENCE OF TRAPPED MAGNETIC-FLUX IN YBA2CU3O7-DELTA

The field-dependences of trapped magnetic fields H-tr(H) in YBa2Cu3O7- delta ceramics were investigated at T = 77-85 K for weak external magn etic fields, H less than or equal to 100 Oe. Non-monotonic H-tr(H) dep endences with several maxima were observed for the first time. The fir st maximum field was H-M1 approximate to 5 Oe, lower by a factor of 20 than the field arising from the penetration of Abrikosov vortices int o grains. The model of interacting loops is proposed to interpret the results. it is shown that suppression of the superconductivity of weak loops by the magnetic field trapped in strong loops can lead to a red istribution of and a decrease in the total trapped magnetic field. The typical loop sizes are estimated.