Regensburg 2010 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 16: CE: Quantum-Critical Phenomena 1

TT 16.5: Vortrag

Dienstag, 23. März 2010, 15:00–15:15, H19

Tuning the Eu valence in EuPd₃B_x by B substitution and pressure - a joint experimental and theoretical study — •Miriam Schmitt¹, Roman Gumeniuk¹, Andreas Leithe-Jasper¹, Walter Schnelle¹, Marcus Schmidt¹, Angela Trapananti², Giuliana Aquilanti², Ulrich Schwarz¹, and Helge Rosner¹ — ¹MPI for Chemical Physics of Solids, Dresden, Germany — ²European Synchrotron Radiat Facil, Grenoble, France

Valence changes induced by doping as well as internal or external pressure often lead to quantum critical phenomena. For EuPd₃B_x, an isostructural phase transition upon B substitution, attended by a change of its magnetic properties, was predicted by band structure theory [1]. According to our calculational results, the phase transition in EuPd₃B_x can be explained by a change of the Eu valence related to a change of the 4f occupation. Upon B insertion, the Eu³⁺ in EuPd₃ changes to Eu²⁺ in EuPd₃B_x (x ≥ 0.2). By applying pressure this effect can be reversed, driving a magnetic Eu²⁺ to a non magnetic Eu³⁺ state. To challenge the prediction of the transitions we carried out XRD and XAS measurements for different B contents as well as for a fixed B content under high pressure. To elucidate the origin of the magnetic change, the experimental results are complemented by density functional based ab-initio band structure calculations using the LDA+U approach (to include strong electron correlations of 4f electrons) and the coherent potential approximation (CPA, to describe substitutional disorder).

[1] C. Loison et al., Phys. Rev. B 75, 205135 (2007).