title: Hamiltonian of the V15 spin system from first-principles density-functional calculations.
abstract: We report first-principles all-electron density-functional-based studies of the electronic structure, magnetic ordering, and anisotropy for the V15 molecular magnet. From these calculations, we determine a Heisenberg Hamiltonian with five antiferromagnetic and one ferromagnetic exchange couplings. We perform direct diagonalization to determine the temperature dependence of the susceptibility. This Hamiltonian reproduces the experimentally observed spin S = 1/2 ground state and low-lying S = 3/2 excited state. A small anisotropy term is necessary to account for the temperature independent part of the magnetization curve.
authors.affiliation: Center for Computational Materials Science, Code 6390, Naval Research Laboratory, Washington, D.C. 20375, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kortus
authors.forename: C S
authors.initials: CS
authors.lastname: Hellberg
authors.forename: M R
authors.initials: MR
authors.lastname: Pederson