Ab initio determination of an extended Heisenberg Hamiltonian in CuO2 layers
Laboratoire de Physique Quantique, IRSAMC, Université Paul Sabatier, 31062 Toulouse, France
Corresponding author: a email@example.com
Published online: 15 June 2001
Accurate ab initio calculations on embedded Cu4O12 square clusters, fragments of the La2CuO4 lattice, confirm a value of the nearest neighbor antiferromagnetic coupling (J=124 meV) previously obtained from ab initio calculations on bicentric clusters and in good agreement with experiment. These calculations predict non negligible antiferromagnetic second-neighbor interaction (J'=6.5 meV) and four-spin cyclic exchange (K=14 meV), which may affect the thermodynamic and spectroscopic properties of these materials. The dependence of the magnetic coupling on local lattice distortions has also been investigated. Among them the best candidate to induce a spin-phonon effect seems to be the movement of the Cu atoms, changing the Cu-Cu distance, for which the variation of the nearest neighbor magnetic coupling with the Cu-O distance is cm-1 Å-1.
PACS: 75.30.Et – Exchange and superexchange interactions / 74.25.Ha – Electronic structure / 74.25.Jb – Magnetic properties
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001