Spin-lozenge thermodynamics and magnetic excitations in Na${}_3$RuO${}_4$

Abstract

We report inelastic and elastic neutron scattering, magnetic susceptibility, and heat capacity measurements of polycrystalline sodium ruthenate (Na${}_3$RuO${}_4$). Previous work suggests this material consists of isolated tetramers of $S=3/2$ Ru${}^{5+}$ 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 spin-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, \textit{i.e} double dimers. However, the existence of long-range magnetic order below $T_c\approx 28$ 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.

11 Pages, 10 Figures, Submitted to Phys. Rev. B

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Cited by in corpus (4)

• Antiferromagnetism in the van der Waals layered spin-lozenge semiconductor CrTe3
• Generalization of polarized spin excitations for asymmetric dimeric systems
• Correlated electron metal properties of the honeycomb ruthenate Na${}_2$RuO${}_3$
• Geometrical frustration and incommensurate magnetic order in Na${}_3$RuO${}_4$ with two triangular motifs