Abstract
We report experimental results on the heat conductivity of the spin chain compounds TiOBr and TiOCl for temperatures and magnetic fields up to 14 T. Surprisingly, we find no evidence of a significant magnetic contribution to , which is in stark contrast to recent results on spin chain cuprates. Despite this unexpected result, the thus predominantly phononic heat conductivity of these spin-Peierls compounds exhibits a very unusual behavior. In particular, we observe strong anomalies at the phase transitions and . Moreover, we find an overall but anisotropic suppression of in the intermediate phase which extends even to temperatures higher than . An external magnetic field causes a slight downshift of the transition at and enhances the suppression of up to . We interpret our findings in terms of strong spin-phonon coupling and phonon scattering arising from spin-driven lattice distortions.
- Received 10 February 2010
DOI:https://doi.org/10.1103/PhysRevB.81.144428
©2010 American Physical Society