| Issue |
Europhys. Lett.
Volume 61, Number 6, March 2003
|
|
|---|---|---|
| Page(s) | 803 - 809 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2003-00305-x | |
| Published online | 01 March 2003 | |
Orbital and spin exchange in 
1
Laboratoire Matériaux et Microélectronique de Provence, UMR 6137, Bât. IRPHE Château Gombert - 49 rue Joliot Curie, BP 146, 13384 Marseille Cedex 13, France
2
Centre de Physique Théorique - Luminy Case 907, 13288 Marseille Cedex 9, France
Received:
8
July
2002
Accepted:
24
December
2002
We derive an effective orbital and spin exchange Hamiltonian
using a perturbative approach to study the compound
. We show that the inclusion of the trigonal
crystal field splitting at the oxygen sites leads to the
appearance of antiferromagnetic exchange integrals in deviation
from the Goodenough-Kanamori-Anderson rules for this 90 degree
bond. That gives a microscopic foundation for the recently
observed coexistence of ferromagnetic and antiferromagnetic
couplings in the orbitally frustrated state of
(F. Reynaud et al.
Phys. Rev.
Lett.
86 (2001) 3638).
PACS: 71.27.+a – Strongly correlated electron systems; heavy fermions / 75.10.Dg – crystal field theory and spin Hamiltonians / 75.30.Et – Exchange and superexchange interactions
© EDP Sciences, 2003
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