Distinct itinerant spin-density waves and local-moment antiferromagnetism in an intermetallic ErPd$_2$Si$_2$ single crystal

TL;DR

This study identifies coexisting itinerant and localized antiferromagnetic orders in ErPd₂Si₂, using neutron scattering and transport measurements to distinguish their distinct wave vectors and behaviors, providing insights into complex magnetic phenomena.

Contribution

It demonstrates the coexistence and competition of itinerant and localized magnetic moments in a single crystal, confirming theoretical predictions and offering a new platform for studying mixed magnetic states.

Findings

Two distinct antiferromagnetic modulations identified

Coexistence and competition of localized and itinerant moments observed

Modulations couple differently with the lattice

Abstract

Identifying the nature of magnetism, itinerant or localized, remains a major challenge in condensed-matter science. Purely localized moments appear only in magnetic insulators, whereas itinerant moments more or less co-exist with localized moments in metallic compounds such as the doped-cuprate or the iron-based superconductors, hampering a thorough understanding of the role of magnetism in phenomena like superconductivity or magnetoresistance. Here we distinguish two antiferromagnetic modulations with respective propagation wave vectors of $Q_{\pm}$ = ($H \pm 0.557(1)$, 0, $L \pm 0.150(1)$) and $Q_\text{C}$ = ($H \pm 0.564(1)$, 0, $L$), where $\left(H, L\right)$ are allowed Miller indices, in an ErPd$_2$Si$_2$ single crystal by neutron scattering and establish their respective temperature- and field-dependent phase diagrams. The modulations can co-exist but also compete depending on temperature or applied field strength. They couple differently with the underlying lattice albeit with associated moments in a common direction. The $Q_{\pm}$ modulation may be attributed to localized 4\emph{f} moments while the $Q_\text{C}$ correlates well with itinerant conduction bands, supported by our transport studies. Hence, ErPd$_2$Si$_2$ represents a new model compound that displays clearly-separated itinerant and localized moments, substantiating early theoretical predictions and providing a unique platform allowing the study of itinerant electron behavior in a localized antiferromagnetic matrix.