Orbitally driven spin-singlet dimerization in $S$=1 La${}_4$Ru${}_2$O${}_{10}$

Abstract

Using x-ray absorption spectroscopy at the Ru-$L_{2,3}$ edge we reveal that the Ru${}^{4+}$ ions remain in the $S$=1 spin state across the rare 4d-orbital ordering transition and spin-gap formation. We find using local spin density approximation + Hubbard U (LSDA+U) band structure calculations that the crystal fields in the low temperature phase are not strong enough to stabilize the $S$=0 state. Instead, we identify a distinct orbital ordering with a significant anisotropy of the antiferromagnetic exchange couplings. We conclude that La${}_4$Ru${}_2$O${}_{10}$ appears to be a novel material in which the orbital physics drives the formation of spin-singlet dimers in a quasi 2-dimensional $S$=1 system.

5 pages, 4 figures, and 1 table

References in corpus (2)

• Orbital-assisted metal-insulator transition in VO${}_2$
• A different look at the spin state of Co${}^{3+}$ ions in CoO${}_5$ pyramidal coordination

Cited by in corpus (4)

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• Orbital ordering in the ferromagnetic insulator Cs${}_2$AgF${}_4$ from first principles
• Optical study of MgTi${}_2$O${}_4$: Evidence for an orbital-Peierls state
• Orbital-Driven Electronic Structure Changes and the Resulting Optical Anisotropy of the Quasi-Two-Dimensional Spin Gap Compound La4Ru2O10