Multi-shell contribution to the Dzyaloshinskii-Moriya spiralling in MnSi-type crystals

TL;DR

This paper develops a microscopic to macroscopic model for MnSi-type chiral magnets, highlighting the role of multi-shell Dzyaloshinskii-Moriya interactions in magnetic twisting and chirality reversal.

Contribution

It introduces a detailed analysis of multi-shell DM interactions and their impact on magnetic properties, providing new insights into the mechanisms behind magnetic chirality.

Findings

DM vector components normal to bonds enhance magnetic twist

Interplay of exchange parameters causes chirality reversal

Model explains concentration-induced chirality changes in MnFeGe

Abstract

The transition from the microscopic Heisenberg model to the macroscopic elastic theory is carried out for the chiral magnetics of MnSi-type with the B20 crystal structure. Both exchange and Dzyaloshinskii-Moriya (DM) interactions are taken into account for the first, second, and third magnetic neighbors. The particular components of the DM vectors of bonds are found, which are responsible for (i) the global magnetic twist and (ii) the canting between four different spin sublattices. A possible mechanism for effective reinforcement of the global magnetic twist is suggested: it is demonstrated that the components of the DM vectors normal to corresponding interatomic bonds become very important for the twisting power. The Ruderman-Kittel-Kasuya-Yosida (RKKY) theory is used for model calculation of exchange parameters. It is found that just the interplay between the exchange parameters of several magnetic shells rather than the signs of DM vectors can be responsible for the concentration-induced reverse of the magnetic chirality recently observed in the Mn_(1-x)Fe_xGe crystals.