On the influence of rare earth metals at concentrations between 0.03 and 0.4% on the conductivity of copper at 4.2K

Binary copper alloys of commercial-grade electrolytic copper with Pr, Nd, Sm, Tb, Dy and Er in the concentration ranges 0.03-0.04 and 0.16-0.36 wt.% have been melted under vacuum. The alloys when strain-free by heating at 3500C for 1 h, show an increase in hardness to 679 N mm-2 compared with 517 N mm-2 for pure copper; at 4.2 K the specific electrical conductivity fell from 5550 m Ω-1 mm-2 to 5318 m Ω-1 mm-2 (Sm), and to 4685 m Ω-1 mm-2 (Tb) over the concentration range 0.03-0.04 wt.% rare earth, and to 3541 m Ω--1 mm-2 (Pr) and 1452 m Ω-1 mm-2 (Dy) over the concentration range 0.16-0.36 wt.%. (Auth.)