Electronic correlation in the quasi-two-dimensional electride Y$_2$C

TL;DR

This study investigates the magnetic properties of Y$_2$C, an electride, using muon spin rotation and susceptibility measurements, revealing no static magnetic order and indicating a ground state near the boundary of weak and strong electronic correlations.

Contribution

It provides experimental insights into the magnetic behavior of Y$_2$C, challenging the predicted ferromagnetism and highlighting the role of electronic correlations and defects.

Findings

No static magnetic order observed down to 0.024 K

Presence of paramagnetic moments in poly-crystalline sample

Electronic ground state near the boundary of weak and strong correlations

Abstract

Magnetic properties of the electride compound Y$_2$C were investigated by muon spin rotation and magnetic susceptibility on two samples with different form (poly- and single-crystalline), to examine the theoretically-predicted Stoner ferromagnetism for the electride bands. There was no evidence of static magnetic order in both samples even at temperatures down to 0.024 K. For the poly-crystalline sample, the presence of a paramagnetic moment at Y sites was inferred from the Curie-Weiss behavior of the muon Knight shift and susceptibility, whereas no such tendency was observed in the single-crystalline sample. These observations suggest that the electronic ground state of Y$_2$C is at the limit between weak-to-strong electronic correlation, where onsite Coulomb repulsion is sensitive to a local modulation of the electronic state or a shift in the Fermi level due to the presence of defects/impurities.