HighT_c phase (T_c ∼ 110 K) has been obtained in Bi-Sr-Ca-Cu-O system by partially substituting Bi by Pb. Magnetic hysteresis has been measured as a function of temperature. Critical current densities have been measured at 77 K both by transport and a.c. magnetization method in bulk samples for various concentrations of Pb. The results show that substitution of 15 at % Pb for Bi is most preferable for higher critical current density.

We assume that currents induced by isothermal changes of magnetic field decay logarithmically with time. Incorporating this time dependence into the critical state model, we obtain logarithmic relaxation rate of magnetization as a function of field for the case of an infinite cylinder. We compare these calculations with our earlier calculations on infinite slab geometry.

Studies on the propagation of AC magnetic field through plasma-sprayed superconducting Y₁Ba₂Cu₃O_7−x coatings show that complete shielding is achieved up to a certain critical magnetic field strengthH₀. Increase in the thickness orJ_c of the specimen increases theH₀ value. Flux-trapping occurs in the specimen at high frequencies and the frequency at which it occurs increases with increase in specimenJ_c.

We present DC magnetization data indicating a first-order phase transition in the vortex state of CeRu₂, with the higher entropy phase exhibiting enhanced pinning. Minor hysteresis loops show evidence of supercooling of the higher entropy phase as the phase boundary is crossed both isothermally as well as at constant field. These features are shown to be absent across the Bragg-glass to vortex-glass transition in Bi₂Sr₂CaCu₂O₈. The supercooling is more persistent in the constant field case.