A previously unreported layered spin 1/2 triangular lattice polymorph of TiI3 is described, synthesized under 6 GPa of applied pressure at 900 C, but stable at atmospheric pressure. This air-sensitive material has a CdI2-type layered structure (P-3m1 (#164), a = 4.012 A and c = 6.641 A at 120 K, Z = 1 of Ti0.667I2) with an in-plane triangular lattice, related to that of TiI4 (Ti0.5I2). Although the TiI3 formula is consistent with expectations for a layered honeycomb lattice of spin 1/2 Ti(III), there appears to be disorder in the crystal structure. Magnetic susceptibility and heat capacity measurements suggest that the material undergoes several low temperature phase transitions.
@article{arxiv.2210.00097,
title = {A Layered Spin 1/2 polymorph of titanium triiodide},
author = {Danrui Ni and Ranuri S. Dissanayaka Mudiyanselage and Xianghan Xu and Junsik Mun and Yimei Zhu and Weiwei Xie and R. J. Cava},
journal= {arXiv preprint arXiv:2210.00097},
year = {2022}
}