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arXiv · 2208.14912

Clamping effect on temperature-induced valence transition in epitaxial EuPd$_2$Si$_2$ thin films grown on MgO(001)

Sebastian Kölsch·Alfons Schuck·Olena Fedchenko·Dmitry Vasilyev·Sergeij Chernov·Lena Tkach·Christoph Schlüter·Thiago R. F. Peixoto·Andrii Gloskowski·Hans-Joachim Elmers·Gerd Schönhense·Cornelius Krellner·Michael Huth
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Abstract

Bulk EuPd$_2$Si$_2$ show a temperature-driven valence transisition of europium from $\sim$+2 above 200 K to $\sim$+3 below 100 K, which is correlated with a shrinking by approximatly 2 % of the crystal lattice along the two a-axes. Due to this interconnection between lattice and electronic degrees of freedom the influence of strain in epitaxial thin films is particularly interesting. Ambient X-ray diffraction (XRD) confirms an epitaxial relationship of tetragonal EuPd$_2$Si$_2$ on MgO(001) with an out-of plane c-axis orientation for the thin film, whereby the a-axes of both lattices align. XRD at low temperatures reveals a strong coupling of the thin film lattice to the substrate, showing no abrupt compression over the temperature range from 300 to 10 K. Hard X-ray photoelectron spectroscopy at 300 and 20 K reveals a temperature-independent valence of +2.0 for Eu. The evolving biaxial tensile strain upon cooling is suggested to suppress the valence transition. Instead low temperature transport measurements of the resistivity and the Hall effect in a magnetic field up to 5 T point to a film thickness independent phase transition at 16-20 K, indicating magnetic ordering.

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Sebastian Kölsch, Alfons Schuck, Olena Fedchenko, Dmitry Vasilyev, Sergeij Chernov, Lena Tkach, Christoph Schlüter, Thiago R. F. Peixoto, Andrii Gloskowski, Hans-Joachim Elmers, Gerd Schönhense, Cornelius Krellner, Michael Huth. 2022-08-31. Clamping effect on temperature-induced valence transition in epitaxial EuPd$_2$Si$_2$ thin films grown on MgO(001). https://doi.org/10.1103/physrevmaterials.6.115003

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