Effect of 3d element substitution for Cu on the ac and dc magnetic properties of bulk (Bi, Pb):2223 superconductor

The effect of the partial substitution of Cu by x = 0.02 Fe and x = 0.02 Ni in the (Bi, Pb):2223 superconductor was investigated by ac and dc susceptibility measurements. The linear dependence of intergranular temperature T_p on ac field amplitude agrees with the Müller critical state model. The intergrain pinning force density _J varies influenced by the nature of 3d ions. Measurements of static susceptibility as a function of temperature in Fe and Ni x = 0.02 samples were analysed using a Curie-Weiss law with a temperature independent background. The effective magnetic moment obtained corresponds to a high spin state for both Fe³⁺ and Ni³⁺ ions, which substituted for Cu in the (Bi, Pb):2223 superconductor.