Helicity Selection of the Cycloidal Order in Noncentrosymmetric EuIrGe$_3$

TL;DR

This study investigates the magnetic helicities in EuIrGe3, revealing that cycloidal helicity is dictated by crystal symmetry and Dzyaloshinskii-Moriya interactions, with external magnetic fields influencing domain selection and phase transitions.

Contribution

It demonstrates the unique determination of cycloidal helicity by symmetry and antisymmetric exchange interactions in EuIrGe3, and explores field-induced domain and phase behavior.

Findings

Cycloidal helicity is uniquely determined by crystal symmetry.

External magnetic fields influence domain selection and induce phase transitions.

Transverse conical state is stabilized under certain magnetic field orientations.

Abstract

The magnetic helicities of the cycloidal ordering in EuIrGe$_3$, with a noncentrosymmetric tetragonal structure, have been studied by circularly polarized resonant X-ray diffraction. It is shown that the helicity of each cycloidal domain is uniquely determined and satisfies the symmetry relations of the $C_{4v}$ point group of the crystal structure. The result shows that the cycloidal helicity is determined by the Dzyaloshinskii-Moriya type antisymmetric exchange interaction. The domain selection and the phase transition by the external magnetic field along [100] and [110] have also been studied. It is shown that the cycloidal plane prefers to be perpendicular to the field and the transverse conical state is realized.