Abstract
Combining thermodynamic measurements with theoretical calculations we demonstrate that the iridates (, Li) are magnetically ordered Mott insulators where the magnetism of the effective spin-orbital moments can be captured by a Heisenberg-Kitaev (HK) model with interactions beyond nearest-neighbor exchange. Experimentally, we observe an increase of the Curie-Weiss temperature from for to for , while the ordering temperature remains roughly the same . Using functional renormalization group calculations we show that this evolution of and as well as the low temperature zigzag magnetic order can be captured within this extended HK model. We estimate that is deep in a magnetically ordered regime, while appears to be close to a spin-liquid regime.
- Received 2 June 2011
DOI:https://doi.org/10.1103/PhysRevLett.108.127203
© 2012 American Physical Society