The Coexistence of Superconductivity and Ferromagnetism in (Ce1-xGdx)Ru2–Self-Induced Vortex State–

Electric resistivity, a.c. magnetic susceptibility, magnetization and 157 Gd NMR measurements have been performed in (Ce 1- x Gd x )Ru 2 for x =0.12 and 0.13. The resistivity measurement determines the superconducting transition temperature for x =0.12 and 0.13 to be 4.85 K and 4.4 K, respectively, though both the susceptibility and magnetization show no diamagnetism. An internal field associated with the ferromagnetic order appears in 157 Gd NMR, where the nuclear spin-lattice relaxation time for x =0.12 below 100 mK shows a characteristic temperature dependence for the superconductivity. From these results, it is concluded that the compound with x =0.12 is microscopically in a coexistent state of the superconductivity and the ferromagnetism at low temperature, forming a self-induced vortex state.