We investigate the magnetic properties of Mn adsorbates on Fe(100) in
the regime up to a few monolayers. Magnetic circular dichroism in abso
rption shows long-range ferromagnetic order for the Mn adsorbate, with
antiferromagnetic alignment with respect to the Fe substrate. Element
-specific magnetic domain imaging and hysteresis measurements show tha
t the macroscopic magnetic behavior of the Mn adlayer is fully determi
ned by the Fe substrate. For coverages below 0.5 ML the Mn absorption
spectra show rich structures that are typical for localized d states.
From this the Mn ground state is identified as a mixture of atomiclike
d(5) and d(6) states, with a local spin moment of 4.5 mu(B). However,
the circular dichroism is 2.4 times smaller than expected for this gr
ound state, suggesting disorder within the Mn adsorbate with an ordere
d moment of 1.9 mu(B) B at 120 K. The magnetic signal vanishes near 1
ML coverage. consistent with the theoretically predicted c(2X2) antife
rromagnetic ground state of the monolayer.