A Layered Spin 1/2 polymorph of titanium triiodide

TL;DR

This paper reports the synthesis and characterization of a new layered spin 1/2 titanium iodide polymorph with a triangular lattice, exhibiting low-temperature phase transitions and structural disorder.

Contribution

It introduces a novel layered TiI3 polymorph synthesized under high pressure, expanding the understanding of titanium iodide structures and their magnetic properties.

Findings

Synthesized under 6 GPa at 900°C, stable at atmospheric pressure.

Displays multiple low-temperature phase transitions.

Has a layered CdI2-type structure with structural disorder.

Abstract

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.