Spin gap formation in the quantum spin systems TiOX, X=Cl and Br

TL;DR

This paper investigates the spin gap formation in layered quantum spin systems TiOCl and TiOBr, linking structural distortions to magnetic transitions and analyzing changes in magnetic exchange interactions.

Contribution

It provides new insights into how structural distortions influence magnetic properties and spin gap formation in TiOX compounds through experimental and theoretical analysis.

Findings

Transition temperatures relate to octahedral distortion and layer separation.

Band structure calculations connect local coordination to magnetic dimensionality.

Magnetic susceptibility suggests larger exchange changes than Raman scattering indicates.

Abstract

In the layered quantum spin systems TiOCl and TiOBr the magnetic susceptibility shows a very weak temperature dependence at high temperatures and transition-induced phenomena at low temperatures. There is a clear connection of the observed transition temperatures to the distortion of the octahedra and the layer separation. Band structure calculations point to a relation of the local coordinations and the dimensionality of the magnetic properties. While from magnetic Raman scattering only a small decrease of the magnetic exchange by -5-10% is derived comparing TiOCl with TiOBr, the temperature dependence of the magnetic susceptibility favors a much bigger change.