The nature of ferromagnetism in the chiral helimagnet $Cr_{1/3}NbS_{2}$

TL;DR

This study investigates the electronic structure of the chiral helimagnet $Cr_{1/3}NbS_{2}$, revealing complex hybridized states and challenging existing theories about its magnetic and transport properties, with implications for spintronic applications.

Contribution

The paper provides new insights into the electronic structure and magnetic interactions in $Cr_{1/3}NbS_{2}$ using experimental measurements and density functional theory, highlighting a non-perturbative Hund's exchange mechanism.

Findings

Fermi surface comprises strongly hybridized Nb- and Cr- derived states.

Spectral weight near the Fermi level increases below $T_{C}$.

Large nearest-neighbor exchange energy suggests a Hund's exchange interaction.

Abstract

The chiral helimagnet, $Cr_{1/3}NbS_{2}$, hosts exotic spin textures, whose influence on the magneto-transport properties, make this material an ideal candidate for future spintronic applications. To date, the interplay between macroscopic magnetic and transport degrees of freedom is believed to result from a reduction in carrier scattering following spin order. Here, we present electronic structure measurements through the helimagnetic transition temperature, $T_{C}$ that challenges this view by showing a Fermi surface comprised of strongly hybridized Nb- and Cr- derived electronic states, and spectral weight in proximity to the Fermi level to anomalously increases as temperature is lowered below $T_{C}$. These findings are rationalized on the basis of first principle, density functional theory calculations, which reveal a large nearest-neighbor exchange energy, suggesting the interaction between local spin moments and hybridized Nb- and Cr- derived itinerant states to go beyond the perturbative interaction of Ruderman-Kittel-Kasuya-Yosida, suggesting instead a mechanism rooted in a Hund's exchange interaction.