We report ab initio quantum chemical cluster calculations of the chain (J_a) and the largest interchain (J_b) Heisenberg exchange of the chain cuprates Ca_2CuO_3 and Sr_2CuO_3. We find that J_a is comparable to the in-plane J in layered cuprates and J_a/J_b ~250-400. Using recent theory we obtain close agreement with experiment for the staggered moments and the critical temperatures. This implies that T_N does not depend on the third parameter J_c << J_b, and cannot be calculated using spin-wave theory. We propose an explanation for this interms of a 1D->2D cross-over.
@article{arxiv.cond-mat/9809249,
title = {Ab initio determination of exchange integrals and Neel temperature in the chain cuprates},
author = {A. B. van Oosten and F. Mila},
journal= {arXiv preprint arXiv:cond-mat/9809249},
year = {2009}
}
Comments
ps, 19 pages. To appear in Chemical Physics Letters