MAGNETISM OF EPITAXIAL 3D-TRANSITION-METAL MONOLAYERS ON GRAPHITE

We have investigated the magnetism of hexagonal 3d-metal monolayers, e pitaxially adsorbed on the graphite (0001) surface, by spin-polarized electronic-structure calculations using the tight-binding linear muffi n-tin orbital method. The calculations have been carried out in ferrom agnetic, antiferromagnetic, and ferrimagnetic configurations for both adsorbed and unsupported monolayers. We find that the V monolayers are nonmagnetic and that the Fe, Co, and Ni monolayers are ferromagnetic. For the Mn monolayers, antiferromagnetic and ferrimagnetic configurat ions are more stable than the ferromagnetic one. For the unsupported C r monolayer, antiferromagnetic and ferrimagnetic configurations exist, but they are almost degenerate with the nonmagnetic solution. This is due to the frustration of the antiferromagnetic nearest-neighbor coup ling on the hexagonal lattice. The magnetic moments of the adsorbed mo nolayers are substantially reduced from their unsupported monolayer va lues and vanish completely in the case of Cr.