From magnetic order to valence-change crossover in EuPd$_2$(Si$_{1-x}$Ge$_x$)$_2$ using He-gas pressure

Medientyp: E-Artikel
Titel: From magnetic order to valence-change crossover in EuPd$_2$(Si$_{1-x}$Ge$_x$)$_2$ using He-gas pressure
Beteiligte: Wolf, Bernd; Spathelf, Felix; Zimmermann, Jan; Lundbeck, Theresa; Peters, Marius; Kliemt, Kristin; Krellner, Cornelius; Lang, Michael
Erschienen: Stichting SciPost, 2023
Erschienen in: SciPost Physics Proceedings
Sprache: Nicht zu entscheiden
DOI: 10.21468/scipostphysproc.11.022
ISSN: 2666-4003
Schlagwörter: General Medicine ; General Chemistry
Entstehung:
Anmerkungen:
Beschreibung: <jats:p>We present results of magnetic susceptibility and thermal expansion measurements performed on high-quality single crystals of EuPd<jats:inline-formula><jats:alternatives><jats:tex-math>_2</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mn>2</mml:mn></mml:msub></mml:math></jats:alternatives></jats:inline-formula>(Si<jats:inline-formula><jats:alternatives><jats:tex-math>_{1-x}</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:math></jats:alternatives></jats:inline-formula>Ge<jats:inline-formula><jats:alternatives><jats:tex-math>_x</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mi>x</mml:mi></mml:msub></mml:math></jats:alternatives></jats:inline-formula>)<jats:inline-formula><jats:alternatives><jats:tex-math>_2</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mn>2</mml:mn></mml:msub></mml:math></jats:alternatives></jats:inline-formula> for 0 <jats:inline-formula><jats:alternatives><jats:tex-math>\leq x \leq</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>≤</mml:mo><mml:mi>x</mml:mi><mml:mo>≤</mml:mo></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> 0.2 and temperatures 2 K <jats:inline-formula><jats:alternatives><jats:tex-math>\leq T \leq</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>≤</mml:mo><mml:mi>T</mml:mi><mml:mo>≤</mml:mo></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> 300 K. Data were taken at ambient pressure and finite He-gas pressure <jats:inline-formula><jats:alternatives><jats:tex-math>p</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math></jats:alternatives></jats:inline-formula><jats:inline-formula><jats:alternatives><jats:tex-math>\leq</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>≤</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 0.5 GPa. For <jats:inline-formula><jats:alternatives><jats:tex-math>x = 0</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>x</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> and ambient pressure we observe a pronounced valence-change crossover centred around <jats:inline-formula><jats:alternatives><jats:tex-math>T'_V</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi><mml:msub><mml:mi>′</mml:mi><mml:mi>V</mml:mi></mml:msub></mml:mrow></mml:math></jats:alternatives></jats:inline-formula><jats:inline-formula><jats:alternatives><jats:tex-math>\approx</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>≈</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 160 K with a non-magnetic ground state. This valence-change crossover is characterized by an extraordinarily strong pressure dependence of d<jats:inline-formula><jats:alternatives><jats:tex-math>T'_V</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi><mml:msub><mml:mi>′</mml:mi><mml:mi>V</mml:mi></mml:msub></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> /d<jats:inline-formula><jats:alternatives><jats:tex-math>p</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math></jats:alternatives></jats:inline-formula> = (80 <jats:inline-formula><jats:alternatives><jats:tex-math>\pm 10)</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mo>±</mml:mo><mml:mn>10</mml:mn><mml:mo stretchy="false" form="postfix">)</mml:mo></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> K/GPa. We observe a shift of <jats:inline-formula><jats:alternatives><jats:tex-math>T'_V</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi><mml:msub><mml:mi>′</mml:mi><mml:mi>V</mml:mi></mml:msub></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> to lower temperatures with increasing Ge-concentration, reaching <jats:inline-formula><jats:alternatives><jats:tex-math>T'_V</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>T</mml:mi><mml:msub><mml:mi>′</mml:mi><mml:mi>V</mml:mi></mml:msub></mml:mrow></mml:math></jats:alternatives></jats:inline-formula><jats:inline-formula><jats:alternatives><jats:tex-math>\approx</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>≈</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 90 K for <jats:inline-formula><jats:alternatives><jats:tex-math>x = 0.1</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>x</mml:mi><mml:mo>=</mml:mo><mml:mn>0.1</mml:mn></mml:mrow></mml:math></jats:alternatives></jats:inline-formula>, while still showing a non-magnetic ground state. Remarkably, on further increasing <jats:inline-formula><jats:alternatives><jats:tex-math>x</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>x</mml:mi></mml:math></jats:alternatives></jats:inline-formula> to 0.2 we find a stable Eu<jats:inline-formula><jats:alternatives><jats:tex-math>^{(2+\delta)+}</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi /><mml:mrow><mml:mrow><mml:mo stretchy="true" form="prefix">(</mml:mo><mml:mn>2</mml:mn><mml:mo>+</mml:mo><mml:mi>δ</mml:mi><mml:mo stretchy="true" form="postfix">)</mml:mo></mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math></jats:alternatives></jats:inline-formula> valence with long-range antiferromagnetic order below <jats:inline-formula><jats:alternatives><jats:tex-math>T_N</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>T</mml:mi><mml:mi>N</mml:mi></mml:msub></mml:math></jats:alternatives></jats:inline-formula> = (47.5 <jats:inline-formula><jats:alternatives><jats:tex-math>\pm</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>±</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 0.1) K, reflecting a close competition between two energy scales in this system. In fact, by the application of hydrostatic pressure as small as 0.1 GPa, the ground state of this system can be changed from long-range antiferromagnetic order for <jats:inline-formula><jats:alternatives><jats:tex-math>p</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math></jats:alternatives></jats:inline-formula><jats:inline-formula><jats:alternatives><jats:tex-math>&#60;</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo><</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 0.1 GPa to an intermediate-valence state for <jats:inline-formula><jats:alternatives><jats:tex-math>p</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math></jats:alternatives></jats:inline-formula><jats:inline-formula><jats:alternatives><jats:tex-math>\geq</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>≥</mml:mo></mml:math></jats:alternatives></jats:inline-formula> 0.1 GPa.</jats:p>
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