NMR Study on the Coexistence of Superconductivity and Ferromagnetism in (Ce1-xGdx)Ru2

Spin echo NMR and ac susceptibility measurements have been performed at 60 mK∼4.2 K in (Ce 1- x Gd x )Ru 2 . The sharp superconducting transition is confirmed for x ≦0.110. The NMR signals associated with the ferromagnetically ordered Gd atoms are observed down to x =0.105 in zero external field and to x =0.095 with applying field. The hyperfine field at Gd site changes as -206+88· x kOe. The intensity of the signal in zero field decreased rapidly in accordance with the appearance of superconductivity. The temperature, concentration and external field dependence of the transverse relaxation time T 2 show that T 1 is governed mainly by the Weger mechanism. The rapid increase of T 1 with lowering temperature for 0.105≦ x ≦0.110 indicates a possible appearance of small energy gap associated with superconducting state. The results support the coexistence of superconductivity and ferromagnetism.