Rotational modes in molecular magnets with antiferromagnetic Heisenberg exchange - art. no. 014418

In an effort to understand the low-temperature behavior of recently synthes ized molecular magnets, we present numerical evidence for the existence of a rotational band in systems of quantum spins interacting with nearest-neig hbor antiferromagnetic Heisenberg exchange. While this result has previousl y been noted for ring arrays with an even number of spin sites, we find tha t it also applies for rings with an odd number of sites as well as for all of the polytope configurations we have investigated (tetrahedron, cube, oct ahedron, icosahedron, triangular prism, and axially truncated icosahedron). It is demonstrated how the rotational band levels can, in many cases, be a ccurately predicted using the underlying sublattice structure of the spin a rray. We illustrate how the characteristics of the rotational band can prov ide valuable estimates for the low-temperature magnetic susceptibility.