Magnetic transition inMnn(n=2–8)clusters

Theoretical electronic structure studies on ${\mathrm{Mn}}_n$ $(n=2\mathrm{}–8)$ clusters have been carried out using a linear-combination-of-atomic-orbitals–molecular-orbital approach within the density-functional formalism. It is shown that ${\mathrm{Mn}}_2$ and ${\mathrm{Mn}}_3$ have energetically close ferromagnetic and antiferromagnetic or frustrated antiferromagnetic solutions. ${\mathrm{Mn}}_4,$ ${\mathrm{Mn}}_5,$ ${\mathrm{Mn}}_6,$ ${\mathrm{Mn}}_7,$ and ${\mathrm{Mn}}_8$ are all ferromagnetic with moments of 20, 23, 26, 29, and 32${\mu }_B.$ The appearance of ferromagnetic character is shown to be accompanied by bonding between minority d states. The relation between geometry and multiplicity and the possibility of closely spaced multiplet states are discussed.