Abstract
We report inelastic and elastic neutron scattering, magnetic susceptibility, and heat capacity
measurements of polycrystalline sodium ruthenate (Na3RuO4). Previous work suggests this material
consists of isolated tetramers of S = 3/2 Ru5+ ions in a so-called �lozenge� configuration. Using
a Heisenberg antiferromagnet Hamiltonian, we analytically determine the energy eigenstates for
general spin S. From this model, the neutron scattering cross-sections for excitations associated
with spin-3/2 tetramer configurations is determined. Comparison of magnetic susceptibility
and inelastic neutron scattering results shows that the proposed �lozenge� model is not distinctly
supported, but provides evidence that the system may be better described as a pair of non-interacting
inequivalent dimers, i.e double dimers. However, the existence of long-range magnetic order below
Tc ≈ 28 K immediately questions such a description. Although no evidence of the lozenge model is
observed, future studies on single crystals may further clarify the appropriate magnetic Hamiltonian.
