Strong enhancement of magnetic ordering temperature and structural/valence transitions in EuPd3S4 under high pressure

TL;DR

This study demonstrates that applying high pressure to EuPd3S4 significantly increases its magnetic ordering temperature and induces structural and valence transitions, revealing pressure as a powerful tool to tune its properties.

Contribution

It provides the first comprehensive high-pressure analysis linking magnetic, structural, and valence changes in EuPd3S4, highlighting the interplay between these phenomena.

Findings

TN increases from 2.8 K to 23.5 K under pressure

Structural transition from cubic to tetragonal occurs around 20-32 GPa

Eu valence shifts from mixed to fully Eu3+ at ~28 GPa

Abstract

We present a comprehensive study of the mixed valent compound, EuPd3S4, by electrical transport, X-ray diffraction, time-domain 151Eu synchrotron M\"ossbauer spectroscopy, and X-ray absorption spectroscopy measurements under high pressure. The electrical transport measurements show that the antiferromagnetic ordering temperature, TN, increases rapidly from 2.8 K at ambient pressure to 23.5 K at ~19 GPa and plateaus between ~19 and ~29 GPa after which no anomaly associated with TN is detected. A pressure-induced first order structural transition from cubic to tetragonal is observed, with a rather broad coexistence region (~20 GPa to ~32 GPa) that corresponds to the TN plateau. M\"ossbauer spectroscopy measurements show a clear valence transition from approximately 50:50 Eu2+:Eu3+ to fully Eu3+ at ~28 GPa, consistent with the vanishing of the magnetic order at the same pressure. X-ray absorption data show a transition to a fully trivalent state at a similar pressure. Our results show that pressure first greatly enhances TN, most likely via enhanced hybridization between the Eu 4f states and the conduction band, and then, second, causes a structural phase transition that coincides with the conversion of the europium to a fully trivalent state.