Muon-spin relaxation measurements on the dimerized spin-1/2 chains NaTiSi2O6 and TiOCl

TL;DR

This study uses muon-spin relaxation and magnetic susceptibility to investigate the spin gaps and magnetic properties of two dimerized spin-1/2 chain compounds, NaTiSi2O6 and TiOCl, revealing temperature-independent and thermally activated spin gaps respectively.

Contribution

It provides detailed measurements of spin gaps and magnetic fluctuations in NaTiSi2O6 and TiOCl, highlighting differences in their temperature dependence and structural influences.

Findings

NaTiSi2O6 has a temperature-independent spin gap of 660K.

TiOCl exhibits a thermally activated spin gap of 420K below 67K.

Muon spin relaxation and magnetic susceptibility methods yield consistent estimates of spin gaps.

Abstract

We report muon spin relaxation (muSR) and magnetic susceptibility investigations of two Ti3+ chain compounds which each exhibit a spin gap at low temperature, NaTiSi2O6 and TiOCl. From these we conclude that the spin gap in NaTiSi2O6 is temperature independent, with a value of 2*Delta=660(50)K, arising from orbital ordering at Too = 210K; the associated structural fluctuations activate the muon spin relaxation rate up to temperatures above 270K. In TiOCl we find thermally activated spin fluctuations corresponding to a spin gap 2*Delta=420(40)K below Tc1=67K. We also compare the methods used to extract the spin gap and the concentration of free spins within the samples from muSR and magnetic susceptibility data.