First-principles theoretical investigations of the noncollinearity of atomic spin moments in manganese clusters have been carried out within a gradient-corrected density-functional approach. Our studies on ${\mathrm{Mn}}_5$ and ${\mathrm{Mn}}_6$ include investigation of both collinear and noncollinear arrangements. It is shown that while the atomic structure of the ground state of ${\mathrm{Mn}}_5$ is a triangular bipyramid, the collinear and noncollinear arrangements have comparable energies and hence are degenerate. For ${\mathrm{Mn}}_6$, while the ground state has a square bipyramid arrangement, the noncollinear configuration is most stable making it the smallest cluster to feature a noncollinear ground state. The results are discussed in view of the recent experimental Stern-Gerlach profiles.

• Received 4 February 2005

DOI:https://doi.org/10.1103/PhysRevB.72.014435