EFFECTS OF PARAMAGNETIC IMPURITIES ON SUPERCONDUCTING PROPERTIES IN LA3-XGDXAL SYSTEM

Effects of the magnetic impurity on superconducting properties were investigated on the La3−xGd xAl system. The superconducting transition temperature Tc, the upper critical field Hc2 and the magnetic susceptibility in the normal state were measured for various concentrations of gadolinium. A remarkable departure of the T c versus impurity concentration curve from the Abrikosov-Gor'kov curve was found in the region of high impurity concentrations (>0.4 at.%GD). Magnetic susceptibility versus temperature curves of compounds with Gd concentrations large enough to suppress the superconductivity showed no peak above 4.2°K. The Hc2 versus temperature curve of the compound with 0.3 at.%Gd crossed the curve of La3 Al. The upper critical field at 0°K, Hc2(0), had a maximum at a certain Gd concentration near La3 Al. This fact is qualitatively explained by the theory of Fulde-Maki. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.