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

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.

7 pages, 7 Figures, 1 Table