MU-SR AND VORTEX PINNING IN BI2SR2(CA1-XGDX)CU2OY

We present transverse field muSR and bulk magnetisation studies on pow ders of Bi2Sr2(Ca1-xGdx)Cu2Oy for 0 less-than-or-equal-to x<0.5. We ha ve found that the effective pinning decreases rapidly with x even for values of x for which T(c) remains unchanged. We have interpreted this decrease in terms of changes in lambda(ab) (obtained from muSR) which cause a decrease in vortex-vortex interactions. The field distributio n spectra in these superconductors have been obtained using a maximum entropy analysis and are found to agree with the calculations by Harsh man et al.