  SQUID magnetometry and polarised neutron reflectivity measurements have been
employed to characterise the magnetic properties of U/Fe, U/Co and U/Gd
multilayers. The field dependence of the magnetisation was measured at 10K in
magnetic fields from -70kOe to 70kOe. A temperature dependent study of the
magnetisation evolution was undertaken for a selection of U/Gd samples. PNR was
carried out in a field of 4.4kOe for U/Fe and U/Co samples (at room
temperature) and for U/Gd samples (at 10K). Magnetic 'dead' layers of about 15
Angstrom were observed for U/Fe and U/Co samples, consistent with a picture of
interdiffused interfaces. A large reduction in the magnetic moment, constant
over a wide range of Gd layer thicknesses, was found for the U/Gd system (about
4 Bohr magnetons compared with 7.63 for the bulk metal). This could be
understood on the basis of a pinning of Gd moments arising from a column-like
growth mechanism of the Gd layers. A study of the effective anisotropy suggests
that perpendicular magnetic anisotropy could occur in multilayers consisting of
thick U and thin Gd layers. A reduction in the Curie temperature was observed
as a function of Gd layer thickness, consistent with a finite-size scaling
behaviour.
