S=1/2 chains and spin-Peierls transition in TiOCl

TL;DR

This paper investigates TiOCl as a layered S=1/2 Mott insulator, revealing orbital ordering that creates quasi-one-dimensional spin chains and demonstrating a high-energy spin-Peierls transition, with impurity effects modeled by chain breaking.

Contribution

It provides a combined experimental and theoretical analysis showing TiOCl as a new high-energy spin-Peierls system with orbital ordering-induced chains.

Findings

Orbital ordering leads to quasi-1D spin chains.

TiOCl exhibits a spin-Peierls transition at a high energy scale.

Impurity effects are explained by broken finite chains.

Abstract

We study TiOCl as an example of an S=1/2 layered Mott insulator. From our analysis of new susceptibility data, combined with LDA and LDA+U band structure calculations, we conclude that orbital ordering produces quasi-one-dimensional spin chains and that TiOCl is a new example of Heisenberg-chains which undergo a spin-Peierls transition. The energy scale is an order of magnitude larger than that of previously known examples. The effects of non-magnetic Sc impurities are explained using a model of broken finite chains.