Coexistence of superconductivity and magnetic ordering in the borocarbide superconducting system

The investigation of the intermetallic compounds Y1-xRExNi2B2C and Y1-xRExP d5B3C0.4 (RE=Gd, Dy, Ho, Er; 0 less than or equal to x less than or equal t o 1.0) demonstrates that the coexistence of the long-range-magnetic-orderin g and the superconductivity is possible The normal-state magnetic susceptib ility shows a Curie-Weiss-like temperature dependence and a small paramagne tic Curie temperature. The value of the effective moment is close to that o f the free RE+3 ion. Both results suggest that the coupling between the con duction electron and magnetic ion is not strong, but the coupling is still strong enough to cause the depression of superconductivity. The Abrikosov-G or'kov magnetic pair-breaking theory can be applied to those systems. The c orresponding magnetic-ordering temperature increases with increasing magnet ic moment concentration while the superconducting transition temperature de creases. The long-range-magnetic-ordering is mainly caused by the Ruderman- Kittel-Kasuya-Yosida indirect exchange interaction via conduction electrons . This indirect exchange coupling strongly depends on the concentration of RE+3-moment and de Gennes factor. (C) 2001 Elsevier Science Ltd. All rights reserved.