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Abstract:
We have performed inelastic neutron scattering (INS) experiments to
study the spin dynamics and search for crystalline-electric-field (CEF)
excitations in the antiferromagnetic heavy-fermion superconductor
UPd2Al3. The low-energy-transfer spectra are predominantly characterized
by a quasielastic Lorentzian (weighted by the detailed balance factor)
with a residual line width of approximately 5 meV. For uranium-based
intermetallics, this is an unusually small line width and UPd2Al3 is one
of the rare examples of 5f-electron systems whose residual line width
corresponds to the macroscopically estimated Kondo lattice temperature.
However, significant deviations from this fit suggest additional
inelastic contributions that persist up to T = 150 K, i.e. 10T(N). This
additional scattering may be attributed to the presence of CEF
excitations or intersite magnetic correlations. A survey of the
scattering within the whole accessible momentum-energy space provides
further evidence for the existence of these inelastic magnetic
intensities. We find a surprisingly good agreement between the
excitation energies of our neutron scattering spectra and a CEF-level
scheme proposed on the basis of magnetic susceptibility and specific
heat measurements.
