M. Kyogaku et al., NMR AND NQR STUDIES OF MAGNETISM AND SUPERCONDUCTIVITY IN THE ANTIFERROMAGNETIC HEAVY-FERMION SUPERCONDUCTORS UM2AL3 (M=NI AND PD), Journal of the Physical Society of Japan, 62(11), 1993, pp. 4016-4030
Both magnetic and superconducting characteristics of the new heavy fer
mion superconductors (HFS), UNi2Al3 and UPd2Al3 have been investigated
extensively by means of Al-27 NMR and NQR. Systematic studies of the
nuclear-spin-lattice relaxation time T1, the Knight shift and the spec
trum of Al-27 have revealed different types of magnetic fluctuations a
nd spin structure between these two compounds. UNi2Al3 shows a band-ty
pe itinerant antiferromagnetic behavior, while UPd2Al3 belongs to a he
avy fermion antiferromagnet with an ordinary size of U-derived moment.
In the superconducting state, the relaxation behavior in UPd2Al3 is s
imilar to those observed in the other HFS reported so far, providing a
n evidence for an unconventional anisotropic superconductivity with li
ne of gap zeros on the Fermi surface as well. Knight shift has been fo
und to decrease considerably below T(c), showing that the pseudo spin
is well defined, not affected by the impurity scattering.