Studies of flux pinning behaviour in melt-processed ternary (Nd-Eu-Gd)Ba2Cu3Oy superconductors

The flux pinning behaviour of ternary melt-processed (Nd-Eu-Gd)Ba2Cu3Oy sup erconductors is studied with various second-phase defect concentrations usi ng magnetotransport and magnetization measurements. A pronounced field-indu ced bump feature in the resistivity was observed. The dissipation was found to be the thermal activation type. The current-voltage (I-V) characteristi cs over the whole transition temperature regime show a linear flux-flow typ e behaviour at high fields that favours an increase in viscosity in the liq uid phase. However, I-V curves show a change of curvature at low field. The Nd/Ba substitution sites along with second-phase particles refined by the addition of a small amount of Pt are basically responsible for high flux pi nning.