Magnetism and superconductivity in CeCu2(Si1-xGex)(2) probed by CuNQR

We report Cu-NQR results on Ge-doped heavy-fermion superconductor CeCu2 (Si 1-xGex)(2) (0 < x <less than or equal to> 0.2) and undoped Ce0.99Cu2.02Si2. The main effect of the Ge doping is considered to be a negative pressure, since the strength of hybridization decreases by the Ge doping. With increa sing x, the dynamical characteristics of the magnetic order at x = 0 change to more static ones which suggests a localized regime above x similar to 0 .25. From the derived T-X phase diagram, it is suggested that the magnetic and the superconducting phases are almost degenerate in undoped CeCu2Si2. A n exotic interplay between the magnetism characterized by the slow fluctuat ions and the superconductivity is implied in the region of small x.