Lattice pinning of magnetic domains in the helimagnet Ba_2CuGe_2O_7

TL;DR

This paper investigates the lattice pinning of magnetic domains in Ba_2CuGe_2O_7, revealing that both Dzyaloshinskii-Moriya and exchange anisotropies are crucial for explaining experimental observations of helical magnetic order.

Contribution

It demonstrates that including exchange anisotropy alongside DM anisotropy accurately explains the lattice pinning of magnetic domains in Ba_2CuGe_2O_7.

Findings

DM anisotropy alone is insufficient for pinning

Exchange anisotropy restores agreement with experiments

Results clarify the bisection rule in magnetic field

Abstract

The layered magnetic compound Ba_2CuGe_2O_7 exhibits spiral antiferromagnetic order thanks to a Dzyaloshinskii-Moriya (DM) anisotropy that is allowed by crystal symmetry. Here we theoretically examine some finer issues such as the experimentally observed lattice pinning of the propagation vector of helical magnetic domains. We find that DM anisotropy alone would lead to incorrect pinning, but agreement with experiment is restored upon including an additional exchange anisotropy that is also consistent with symmetry. The present results shed light on the so-called bisection rule which has been abstracted from experiment in presence of an in-plane magnetic field.