Local impurities in 2D quantum antiferromagnets
arXiv:cond-mat/9801001 · doi:10.1016/S0304-8853(97)00844-5
Abstract
The two-dimensional quantum Heisenberg antiferromagnet at zero temperature with two kinds of locally frustrating defects - isolated ferromagnetic bonds and impurity spins, is studied. For a quantum spin, coupled antiferromagnetically to the two sublattices, we find a local ground state transition. In the case of a ferromagnetic bond, the local magnetization is found to remain finite even for strong coupling, contrary to previous results, derived within the linear spin-wave approximation. Our results are based on an analytic approach, suitable to treat strong defect-environment interaction, as well as exact diagonalization studies. Technical details and some extension of this work can be found in cond-mat/9712281.
5 pages, REVTex, 2 Postscript figures; presented at the International Conference on Magnetism 97, Cairns; to be published in J. Magn. Magn. Mat. 177-180 (1998)