Orbitally Driven Spin-Singlet Dimerization in S=1 La4Ru2O10

Wu H.

Hu Z.

Burnus T.

Denlinger J.D.

Khalifah P.G.

Mandrus D.G.

Jang L.-Y.

Hsieh H.H.

Tanaka Arata

Liang K.S.

Allen J.W.

Cava R.J.

Khomskii D.I.

Tjeng L.H.

Physical Review Letters

Using x-ray absorption spectroscopy at the Ru-L2,3 edge we reveal that the Ru4+ 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 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 La4Ru2O10 appears to be a novel material in which the orbital physics drives the formation of spin-singlet dimers in a quasi-two-dimensional S=1 system.

eng

American Physical Society

Copyright (c) 2006 American Physical Society.

[ISSN] 0031-9007

[DOI] 10.1103/PhysRevLett.96.256402

[NCID] AA00773679

[DOI] http://dx.doi.org/10.1103/PhysRevLett.96.256402