New Alloy Shows Promise as High‐Field Superconducting Magnet

An alloy of niobium, germanium and aluminum, $Nb0.8(Al0.75Ge0.25)0.2,$ has remained superconducting in a 410‐kG field at a temperature of 4.2 K. The alloy has the highest known transition temperature, 20.7 K. If the alloy can be made into a wire or tape that can maintain a high current density, it could be used to build a high‐field superconducting dc magnet (provided one could make a structure that would hold together under the enormous forces produced by the fields). The best material previously tested, $Nb3Sn,$ has a critical field of about 220 kG at 4.2 K and has been used in commercial magnets for several years.