J(c)-B performance study of an OCMG (Nd-Eu-Gd)-123 material doped by sub-micrometre Gd-211 particles

A concentration profile of Gd2BaCuO5 (Gd-211) fine particles embedded in an oxygen-controlled melt-grown (Nd0.33Eu0.33Gd0.33)Ba2Cu3O7-y (NEG-123) mate rial is studied. The secondary phase had a nominal content of 30 mol% and w as refined by the addition of 0.5 mol% Pt and 1 mol% CeO2. The main concern of this paper is devoted to the variation of the magnetic properties and G d-211 phase distribution in a bulk NEG-123 pellet of 1.8 cm in diameter and 1 cm in height. J(c)(B) dependences deduced from magnetic hysteresis curve s measured by SQUID were analysed with respect to the appearance of the cen tral and second peaks. A successful fit of all the curves by an analytical function composed of two additive contributions representing the central an d second peaks is reported. The separation of these two contributions revea led that the shape of the high-field part of the magnetization curves is mo stly governed by the pinning mechanism(s) responsible for the second peak a nd no 'background' from another source of pinning is involved.