  The structural and electronic properties of the surfaces of Sm(0001) and
Eu/Gd(0001) were studied by scanning tunneling microscopy and spectroscopy at
temperatures between 10 and 110 K. In both systems, an unoccupied surface state
is observed that exhibits a temperature-dependent splitting into two states for
Eu/Gd(0001), while it is unsplit on Sm(0001). This strongly indicates that the
divalent outermost surface layer of Sm(0001) is non-magnetic despite the
antiferromagnetic trivalent Sm substrate. These findings open new opportunities
for magnetic studies of ultra-thin Sm films.
