Raman phonon spectrum of the Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7

TL;DR

This study provides a comprehensive experimental and theoretical analysis of the lattice dynamics in Ba2CuGe2O7, a Dzyaloshinskii-Moriya helimagnet, through Raman spectroscopy and shell-model calculations across a range of temperatures.

Contribution

It offers the first detailed Raman spectral analysis of Ba2CuGe2O7, confirming phonon modes and their vibrational frequencies with theoretical calculations, enriching understanding of its lattice dynamics.

Findings

29 phonon lines observed out of 35

Good agreement between experimental and shell-model frequencies

Provides a complete description of lattice dynamics in Ba2CuGe2O7

Abstract

The Raman spectrum of Ba2CuGe2O7, a tetragonal insulator which develops Dzyaloshinsky- Moriya helical magnetism below TN = 3.2 K, has been detected at temperatures varying from 300 to 80 K in a single crystal, with the radiation polarized either in the ab plane or along the c axis of its tetragonal cell. 29 phonon lines out of the 35 allowed by the Raman selection rules for the present geometry were observed, and their vibrational frequencies were found in overall good agreement with those provided by shell-model calculations. Together with the previous report on the infrared-active phonons [A. Nucara et al., Phys. Rev. B 90, 014304 (2014)] the present study provides an exhaustive description, both experimental and theoretical, of the lattice dynamics in Ba2CuGe2O7.