Clamping effect on temperature-induced valence transition in epitaxial EuPd$_2$Si$_2$ thin films grown on MgO(001)
Abstract
Bulk EuPdSi show a temperature-driven valence transisition of europium from +2 above 200 K to +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 EuPdSi 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.
Keywords
Cite
@article{arxiv.2208.14912,
title = {Clamping effect on temperature-induced valence transition in epitaxial EuPd$_2$Si$_2$ thin films grown on MgO(001)},
author = {Sebastian Kölsch and Alfons Schuck and Olena Fedchenko and Dmitry Vasilyev and Sergeij Chernov and Lena Tkach and Christoph Schlüter and Thiago R. F. Peixoto and Andrii Gloskowski and Hans-Joachim Elmers and Gerd Schönhense and Cornelius Krellner and Michael Huth},
journal= {arXiv preprint arXiv:2208.14912},
year = {2024}
}