Ab initio determination of an extended Heisenberg Hamiltonian in CuO2 layers
نویسنده
چکیده
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 secondneighbor 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 ∆J/∆dCu−O ∼1700 cm Å.
منابع مشابه
Proposal of an extended t-J Hamiltonian for high-Tc cuprates from ab initio calculations on embedded clusters
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