Abstract
Recently, Pfandzelter et al. (1995) reported the first observation of monolayer ferromagnetism of a 4d metal, namely in a Ru monolayer grown on graphite. Using the tight-binding linear-muffin-tin-orbital (TB-LMTO) method we have calculated the electronic and magnetic structure of epitaxial Ru and Rh monolayers on graphite with the experimentally determined atomic density. Monolayers of the other 4d elements were found to be non-magnetic already in the free-standing limit. The magnetic structure of the Ru and Rh monolayers is studied as a function of metal-graphite interlayer distance h. They become magnetic at h = 4.5 a.u. (Ru) and h = 4.8 a.u. (Rh) in a first-order transition. In the assumed p(2 × 2) super-structure, the moments on the “hollow” site atoms are up to four times bigger than those on the “on-top” site atoms. For h > 5.4 a.u. (Ru) and h > 5.1 a.u. (Rh) the site dependence vanishes and the moments of the free monolayers are approximately reached (1.9 μB and 1.2 μB, respectively).
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