Grain Refinement and Enhancement of Critical Current Density in the V0.60Ti0.40 Alloy Superconductor With Gd Addition

The V-Ti alloys are promising materials as alternate to the commercial Nb-based superconductors for high current-high magnetic field applications. However, the critical current density (Jc) of these alloys are somewhat low due to their low grain-boundary density. We show here that grain refinement of the V-Ti alloys and enhancement of the Jc can be achieved by the addition of Gd into the system, which precipitates as clusters along the grain boundaries. Both the Jc and the pinning force density (FP) increase with the increasing Gd content up to 1 at. % Gd, where they are more than 20 times higher than those of the parent V
_0.60
Ti
_0.40
alloy. Introduction of Gd into the system also leads to ferromagnetic (FM) correlations, and the alloys containing more than 0.5 at. % Gd exhibit spontaneous magnetization. In spite of the FM correlations, the superconducting transition temperature increases slightly with Gd-addition.