Magnetic anisotropy and low-energy spin waves in the Dzyaloshinskii-Moriya spiral magnet Ba_2 Cu Ge_2 O_7

TL;DR

This study uses neutron scattering to analyze the magnetic structure and spin waves in Ba_2 Cu Ge_2 O_7, revealing the importance of the KSEA anisotropy term in explaining its magnetic behavior.

Contribution

It refines the magnetic model of Ba_2 Cu Ge_2 O_7 by incorporating the KSEA anisotropy term alongside Dzyaloshinskii-Moriya interactions.

Findings

Magnetic structure and spin wave spectrum depend on field.

KSEA term explains experimental data.

Refined model improves understanding of magnetic anisotropy.

Abstract

New neutron diffraction and inelastic scattering experiments are used to investigate in detail the field dependence of the magnetic structure and low-energy spin wave spectrum of the Dzyaloshinskii-Moriya helimagnet Ba_2 Cu Ge_2 O_7. The results suggest that the previously proposed model for the magnetism of this compound (an ideal sinusoidal spin spiral, stabilized by isotropic exchange and Dzyaloshinskii-Moriya interactions) needs to be refined. Both new and previously published data can be quantitatively explained by taking into account the Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) term, a special magnetic anisotropy term that was predicted to always accompany Dzyaloshinskii-Moriya interactions in insulators.