NMR-STUDY OF WEAK MAGNETISM AND SUPERCONDUCTIVITY IN HEAVY-FERMION SYSTEMS

Using NMR techniques, we have investigated the superconducting and magnetic properties of the heavy-fermion superconductors (HFS), CeCu2Si2, and the recently discovered UM2Al3 (M = Ni and Pd). The NMR studies have deduced that the nature of the magnetism in HFS is varied, whereas the superconducting property possesses a rather common feature. Namely, the nuclear spin-lattice relaxation rate 1/T1 is well described in terms of an anisotropic energy gap model in which the gap vanishes on lines at the Fermi surface with values of 2DELTA/k(B)T(c) = 5.0 and 5.5 for CeCu2Si2 and UPd2Al3, respectively. The unusual superconductivity coexists with the magnetism, regardless of whether it is in a static or a dynamical regime. In contrast, the NMR experiment detected no signature of an anomaly at the superconducting transition temperature in UNi2Al3. The interplay between magnetism and superconductivity is discussed from a comparison with other heavy-fermion superconductors.