Flux Pinning in (Bi_0.9 Pb_0.13)₂Sr₂(Ca_0.98R_0.02)₂Cu₃O_10+δ System (R=Sm, Eu, Gd, Dy, Ca)

The (Bi_0.9 Pb_0.13)₂Sr₂(Ca_0.98R_0.02)₂Cu₃O_10+δ superconductors (R = Sm, Eu, Gd, Dy, Ca) were prepared and the flux pinning effects of all samples were studied using vibrating sample magnetometer. We found that the pinning potential energy U increases but the flux pinning force F_p decreases when the magnetic moment of the rare earth element increases. We believe that this effect may come from the area of normal state resulting from the magnetic moment of the rare earth element which was particularly substituted for the Ca²⁺ ion of our samples.