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arXiv · 2210.03860

Valence and magnetism in $\rm EuPd_3S_4$ and $\rm (Y,La)_xEu_{1-x}Pd_3S_4$

D. H. Ryan·Sergey L. Bud'ko·Brinda Kuthanazhi·Paul C. Canfield
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Abstract

$^{151}$Eu M\"ossbauer spectroscopy shows that yttrium substitution in mixed-valent $\rm EuPd_3S_4$ drives the initial 50:50 mix of Eu$^{3+}$ and Eu$^{2+}$ towards pure Eu$^{2+}$, whereas lanthanum substitution has the opposite effect, but only for substitution levels above 50\%. We find that total valence electron count and chemical pressure effects cannot account for the observed behaviour, however conserving the cell volume provides a consistent description of the changes in the Eu$^{2+}$:Eu$^{3+}$ ratio. Remarkably, lanthanum substitution also leads to a clear transition from static mixed-valent behavior at lower temperatures to dynamic mixed valent behavior at higher temperatures, with the onset temperature monotonically increasing with Eu content and extrapolating to a value of $\sim$340~K for the pure $\rm EuPd_3S_4$ compound. Magnetic order persists at least as far as x=0.875 in both series, despite the drastic reduction in the amount of moment-carrying Eu$^{2+}$ ions.

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D. H. Ryan, Sergey L. Bud'ko, Brinda Kuthanazhi, Paul C. Canfield. 2022-10-08. Valence and magnetism in $\rm EuPd_3S_4$ and $\rm (Y,La)_xEu_{1-x}Pd_3S_4$. https://doi.org/10.1103/physrevb.107.014402

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