We studied the thermodynamics of the one-dimensional J1-J2 spin-1/2 Heisenberg chain for ferromagnetic nearest-neighbor bonds J1 < 0 and frustrating antiferromagnetic next-nearest-neighbor bonds J1 > 0 using full diagonalization of finite rings and a second-order Green-function formalism. Thereby we focus on J2 < |J1|/4 where the ground state is still ferromagnetic, but the frustration influences the thermodynamic properties. We found that their critical indices are not changed by J2. The analysis of the low-temperature behavior of the susceptibility chi leads to the conclusion that this behavior changes from chi \propto T^{-2} at J2 < |J1|/4 to chi \propto T^{-3/2} at the quantum-critical point J2=|J1|/4. Another effect of the frustration is the appearance of an extra low-T maximum in the specific heat C_v(T) for J2 \gtrsim |J1|/8, indicating its strong influence on the low-energy spectrum.
@article{arxiv.0811.3549,
title = {Thermodynamics of the frustrated ferromagnetic spin-1/2 Heisenberg chain},
author = {J. Richter and M. Härtel and D. Ihle and S. -L. Drechsler},
journal= {arXiv preprint arXiv:0811.3549},
year = {2011}
}
Comments
4 pages, 4 figures, paper presented at the HFM2008 conference (Sept. 2008), accepted for the proceedings of HFM2008