High-resolution ac susceptibility and thermal conductivity measurement on Cu2Te2O5X2(X=Br,Cl) single crystals are reported. For Br-sample, sample dependence prevents to distinguish between possibilities of magnetically ordered and spin-singlet ground states. In Cl-sample a three-dimensional transition at 18.5 K is accompanied by almost isotropic behavior of susceptibility and almost switching behavior of thermal conductivity. Thermal conductivity studies suggest the presence of a tremendous spin-lattice coupling characterizing Cl- but not Br-sample. Below the transition Cl-sample is in a complex magnetic state involving AF order but also the elements consistent with the presence of a gap in the excitation spectrum.
@article{arxiv.cond-mat/0307647,
title = {Ground state order and spin-lattice coupling in tetrahedral spin systems Cu2Te2O5X2},
author = {M. Prester and A. Smontara and I. Zivkovic and A. Bilusic and D. Drobac and H. Berger and F. Bussy},
journal= {arXiv preprint arXiv:cond-mat/0307647},
year = {2009}
}
Comments
version accepted for publication in Phys.Rev.B-Rapid Communication