Magnetism of3dtransition-metal adatoms and dimers on graphite

The topic of this work is $3d$ transition metals deposited on a graphite surface. Spin-polarized density-functional calculations are used to obtain the magnetic moments of deposited adatoms and dimers and also their preferred position on the surface. Adatoms in the lower part of the series position themselves above C sites and their magnetic moments are higher than their free atom values, while those in the upper part display smaller moments and prefer a position above the center of a C ring. The atoms in the dimers lie either above neighboring rings or above a line through the centers of C-C bonds at opposite sides of a ring. The moments of most of the dimers are similar to their values as free diatomic molecules. Ni is nonmagnetic on the surface, both as a monomer and as a dimer.