Comment on "Frustrating interactions and broadened magnetic interactions in the edge-sharing CuO_2 chains in La_5 Ca_9 Cu_24 O_41"

Abstract

Using Monte Carlo techniques, we show that the two--dimensional anisotropic Heisenberg model reproducing nicely inelastic neutron scattering measurements on La_5 Ca_9 Cu_24 O_41 (Matsuda et al. [Phys. Rev. B 68, 060406(R) (2003)]) seems to be insufficient to describe correctly measurements on thermodynamic quantities like the magnetization or the susceptibility. Possible reasons for the discrepancy are suggested.

3 pages, 2 EPS figures; part (ii) rewritten, some typos corrected; final version that has been accepted for publication in Phys. Rev. B