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Abstract:
The magnetic and superconducting properties of the new heavy fermion
superconductors (HFS), UNi2Al3 and UPd2Al3 have been investigated by
Al-27 NMR. The magnetic ordering is unambiguously identified by a
significant increase of Al-27 linewidth below T(N) = 4.6 K and an
enhancement of the nuclear-spin-lattice relaxation rate 27(1 / Tl)
around T(N) in UNi2Al3 and by a gradual increase of the linewidth and a
distinct drop of 27(1 / Tl) below T(N) = 14 K in UPd2Al3. Below T(c) =
0.9 K in a magnetic field of 2.8 kOe, no anomalies of 1 / Tl and Knight
shift have been observed in UNi2Al3, whereas the superconductivity in
UPd2Al3 is well evidenced by a significant decrease of both 1 / Tl and
Knight shift below T(c) = 1.8 K in 4.9 kOe. The behavior of 1 / Tl in
UPd2Al3, with no coherence peak just below T(c), is well described down
to 0.65 K by a model of gap zeros on lines at the Fermi surface, being
quite similar to the behavior in HFS reported thus far.
