Superconductivity in Zr2(Co1−xCux)

• The result of the remarkable changes in lattice parameters and superconducting transition temperatures Tc with copper content x in Zr2(Co1−xNix) was found.
• It is implied that the Tcs of Zr2(Co1−xCux) may originate predominantly from the spin density fluctuations.

As judged by X-ray-powder patterns and crystallographic data, the body-centered tetragonal structure of the parent compound Zr2Co is retained in Zr2(Co1−xCux) up to the solubility limit near x = 0.3. Variation of room temperature lattice parameters indicates that parameter a expands linearly with increasing x while c and c/a values decrease linearly with x due to doping with Cu. Magnetic and electrical measurements show that there is a prominent maximum Tc close to x = 0.05. This illustrates that the superconducting transition temperature of the pseudo-binary system Zr2(Co1−xCux) is not a monotonic function of the lattice constants a, c, c/a, or v.