Magnetic Properties of the Melt-Textured (Nd,Eu,Gd)Ba2Cu3Oy Superconductors Doped by Nanoparticles of Refractory Metals

Magnetic data measured on (Nd0.33Eu0.33Gd0.33)Ba2Cu3Oy with 35 mol% of Gd-211 (70 nm size), 1 wt% Ag, and 0.1 mol% of TiO2, Nb2O5, and MoO3 (all 10 nm grain size) were analyzed. These composites exhibited very high critical current density, qualifying them to be the best candidates for use as bulk superconducting magnets. The data were analyzed on the basis of the phenomenological model of two additive contributions from “large” particles and point like defects. The model enables a quantitative evaluation of both pinning categories as to their pinning efficiency under various conditions. The pinning force was analyzed in terms of both this model and the Kramer's scheme.