Investigation of the Spin-Peierls transition in CuGeO_3 by Raman scattering

TL;DR

This study uses Raman scattering to investigate magnetic excitations and phonon modes in CuGeO3 and its substituted variants, revealing detailed behaviors of magnetic excitations across the spin-Peierls transition and disorder effects.

Contribution

It provides new insights into magnetic excitations and phonon interactions in CuGeO3 and substituted compounds through detailed Raman spectroscopy analysis.

Findings

Identification of magnetic excitations below Tsp=14 K

Observation of a broad intensity maximum at 300 cm$^{-1}$ between Tsp and 100 K

Detection of folded phonon modes at 369 and 819 cm$^{-1}$

Abstract

Raman experiments on the spin-Peierls compound CuGeO$_3$ and the substituted (Cu$_{1- x}$,Zn$_x$)GeO$_3$ and Cu(Ge$_{1-x}$,Ga$_x$)O$_3$ compounds were performed in order to investigate the response of specific magnetic excitations of the one-dimensional spin-1/2 chain to spin anisotropies and substitution-induced disorder. In pure CuGeO$_3$, in addition to normal phonon scattering which is not affected at all by the spin-Peierls transition, four types of magnetic scattering features were observed. Below T$_{SP}$=14 K a singlet-triplet excitation at 30 cm$^{-1}$, two-magnon scattering from 30 to 227 cm$^{-1}$ and folded phonon modes at 369 and 819 cm$^{-1}$ were identified. They were assigned by their temperature dependence and lineshape. For temperatures between the spin-Peierls transition T$_{SP}$ and approximately 100 K a broad intensity maximum centered at 300 cm$^{-1}$ is observed.