Incommensurate structure of the spin-Peierls compound TiOCl

TL;DR

This study investigates the incommensurate crystal structure of TiOCl, revealing phase transition characteristics, magnetic field effects, and structural similarities with TiOBr, advancing understanding of spin-Peierls compounds.

Contribution

It provides detailed structural analysis of TiOCl's incommensurate phase and its magnetic field dependence, highlighting competing interactions in the material.

Findings

Incommensurate modulation similar to TiOBr.

First order phase transition with thermal hysteresis.

Magnetic field shifts transition temperature by -0.13 K at 10 T.

Abstract

We report on a detailed single crystal x-ray diffraction study of the unconventional spin-Peierls compound TiOCl. The intermediate phase of TiOCl is characterized by an incommensurate modulation which is virtually identical to that recently found in the homologue compound TiOBr. The first order phase transition between the spin-Peierls ground state and the incommensurate phase reveals the same kind of thermal hysteresis in both, its crystal structure and magnetic susceptibility. A weak, but significant magnetic field effect is found for this phase transition with a field induced shift of the transition temperature of Delta Tc1= -0.13 K for an applied field of B=10 T along the chain direction. The field induced changes of the incommensurate crystal structure are compatible with a scenario of competing intra- and inter-chain interactions.