First-principles density-functional-theory investigations of small ${\mathrm{Mn}}_n$ $(n=2\mathrm{}–7,13)$ clusters reveal a competition between ferromagnetic and antiferromagnetic ordering of atomic magnetic moments. For smaller sizes $(n<~6),$ this competition results in a near degeneracy between the two types of orderings, whereas AF arrangements are clearly favored for larger clusters. The calculations thus predict a size-dependent transition in the magnetic ordering of Mn clusters.

• Received 6 September 2002

DOI:https://doi.org/10.1103/PhysRevA.67.061202