Prof. Alexander Tsirlin
University of Leipzig, Germany

Abstract: CrRhAs and CrNiAs: kagome metals with contrasting magnetism

Metallic compounds with the kagome geometry show various electronic instabilities and host exotic phases at low temperatures. Here, we present an experimental and computational study of the electronic properties of two hitherto unexplored compounds of this type, CrRhAs and CrNiAs. They feature Cr3+ as the magnetic ion, but show dissimilar magnetic behavior. 

CrRhAs is a metallic antiferromagnet with a non-collinear magnetic structure below 150 K and a linear Hall response, yet with the sign change in the Hall coefficient depending on the direction of the applied current. By contrast, CrNiAs is a ferromagnet with the Curie temperature of about 180 K, a sizable anomalous Hall effect, and an additional phase transition around 100 K driven by a strong magnetoelastic effect in this material. Hydrostatic pressure leads to a gradual suppression of ferromagnetic order in CrNiAs. Intriguingly, the paramagnetic phase stabilized above 12 GPa shows a T-linear resistivity that signals the strange-metal behavior extending up to at least 27 GPa. 

Main experimental observations will be contrasted with the calculated electronic structures of CrRhAs and CrNiAs. We argue that both materials show a sizable effective mass and feature moderate electronic correlations with mostly localized Cr magnetic moments, which may be retained even in the paramagnetic state and underlie the intriguing electronic properties of both materials. On the other hand, no flat bands appear near the Fermi level. It renders CrRhAs and CrNiAs rare examples of kagome metals where correlation effects are not driven by the flat bands of the kagome network.