Origin of Incommensurate Magnetic Order in Rare-Earth Magnetic Weyl Semimetals

TL;DR

This study uses first-principles simulations to uncover that in rare-earth magnetic Weyl semimetals, incommensurate magnetic order stems from frustrated superexchange interactions rather than Fermi surface nesting or Dzyaloshinskii-Moriya effects.

Contribution

It reveals the origin of helical magnetic order in rare-earth Weyl semimetals as due to frustrated superexchange, challenging previous assumptions about topological nesting effects.

Findings

Helical order is caused by frustrated isotropic superexchange.

Fermi surface nesting and Dzyaloshinskii-Moriya interactions are not responsible.

Spin Hamiltonian with isotropic exchange reproduces experimental order.

Abstract

We investigate rare-earth magnetic Weyl semimetals through first-principles simulations, analyzing the connection between incommensurate magnetic order and the presence of Weyl nodes in the electronic band structure. Focusing on PrAlSi, NdAlSi, and SmAlSi, we demonstrate that the reported helical ordering does not originate from the nesting of topological features at the Fermi Surface or the Dzyaloshinskii-Moriya interaction. Instead, the helical order arises from frustrated isotropic short-range superexchange between the 4f moments facilitated by pd-hybridization with the main group elements. Employing a spin Hamiltonian with isotropic exchange and single-ion anisotropy we replicate the experimentally observed helical modulation.