Eur. Phys. J. B 43, 29-37 (2005)
https://doi.org/10.1140/epjb/e2005-00024-8

Electronic structure of the Sr_0.4Ca_13.6Cu₂₄O₄₁ incommensurate compound

¹ Laboratoire de Physique Quantique, IRSAMC/UMR 5626, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 4, France
² Laboratoire CRISMAT, ISMRA/CNRS UMR 6508, 6 boulevard du Maréchal Juin, 14050 Caen Cedex, France

Corresponding author: ^a lepetit@ensicaen.fr

Received: 23 September 2004
Published online: 11 February 2005

Abstract

We extracted, from strongly-correlated ab-initio calculations, a complete model for the chain subsystem of the Sr_0.4Ca_13.6Cu₂₄O₄₁ incommensurate compound. A t-J+V model has been determined as a function of the fourth crystallographic parameter τ, for both low and room temperature crystallographic structures. The analysis of the obtained model shows the crucial importance of the structural modulations on the electronic structure through the on-site energies and the magnetic interactions. The structural distortions are characterized by their long range effect on the cited parameters that hinder the reliability of analyses such as BVS. One of the most striking results is the existence of antiferromagnetic nearest-neighbor interactions for metal-ligand-metal angles of 90°. A detailed analysis of the electron localization and spin arrangement is presented as a function of the chain to ladder hole transfer and of the temperature. The obtained spin arrangement is in agreement with antiferromagnetic correlations in the chain direction at low temperature.