Atomic structures and magnetic behavior of Mn clusters

The structures and magnetic properties of Mn clusters containing 13, 15, 19, and 23 atoms have been predicted from ab initio electronic structure calculations. The lowest energy structures of the 13-, 19-, and 23-atom clusters are icosahedral and have ordered spin configurations in which blocks of ferromagnetically coupled spins are antiferromagnetically coupled with each other. The 15-atom cluster is body-centered cubic with antiferromagnetic coupling. The net moments are small and lie in the range of 0.2--1.2μB/atom; however, the average local atomic moments have high values close to 4μB. These results are discussed in light of recent Stern-Gerlach experiments.