Spin fluctuations in CuGeO$_3$ probed by light scattering

TL;DR

This study investigates spin fluctuations in CuGeO$_3$ using Raman scattering, revealing temperature-dependent quasi-elastic scattering linked to energy density fluctuations and analyzing magnetic properties near the spin-Peierls transition.

Contribution

It provides the first detailed Raman scattering analysis of spin fluctuations in CuGeO$_3$ and compares experimental data with theoretical models, highlighting discrepancies.

Findings

Quasi-elastic scattering observed above T_{SP}

Inverse magnetic correlation length scales as (T-T_{SP})^{1/2}

Competing-$J$ model fails to fully explain specific heat and susceptibility

Abstract

We have measured temperature dependence of low-frequency Raman spectra in CuGeO$_3$, and have observed the quasi-elastic scattering in the $(c,c)$ polarization above the spin-Peierls transition temperature. We attribute it to the fluctuations of energy density in the spin system. The magnetic specific heat and an inverse of the magnetic correlation length can be derived from the quasi-elastic scattering. The inverse of the magnetic correlation length is proportional to $(T-T_{SP})^{1/2}$ at high temperatures. We compare the specific heat with a competing-$J$ model. This model cannot explain quantitatively both the specific heat and the magnetic susceptibility with the same parameters. The origin of this discrepancy is discussed.