Analysis of the phonon spectrum in the titanium oxyhalide TiOBr
Journal
Journal of Physics Condensed Matter
Journal Volume
16
Journal Issue
30
Pages
5583-5596
Date Issued
2004
Author(s)
Abstract
We present the electrodynamic response of TiOBr, which undergoes a transition to a spin-singlet ground state for temperatures below TC1 = 28 K. The temperature evolution of the phonon anomalies indicates, like in TiOCl, an extended fluctuation regime, extending well above TC1. At low frequencies, the spectral weight is progressively suppressed by decreasing the temperature, suggesting the formation of a spin-gap and a considerable electron-phonon coupling. A comparison of the two oxyhalides shows a weaker interplane coupling and reduced dimensionality for TiOBr that enhances fluctuations and shifts the ordering temperatures to lower values. In the fluctuation regime the temperature dependences of some phonon parameters track the temperature evolution of the magnetic susceptibility.
Type
journal article