Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.3: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Boron induced change of valence state of Eu in EuPd₃B_x (0 ≤ x ≤ 0.55) — •Roman Gumeniuk, Claire Loison, Andreas Leithe-Jasper, Walter Schnelle, Ulrich Burkhardt, Marcus Schmidt, Miriam Schmitt, Ulrich Schwarz, and Helge Rosner — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden, Germany

A detailed experimental and theoretical study of the solubility of B in cubic EuPd₃ (AuCu₃ structure type) and its influence on the physical properties is presented here. Theoretical calculations (LDA + U + CPA method) predict in EuPd₃B_x a change of non-magnetic 4f⁶ Eu to magnetic 4f⁷ Eu for a boron content of x > 0.2 together with an anomaly in the unit cell volume. At 950^oC the incorporation of B in the structure of EuPd₃B_x is possible up to x = 0.55, as can be concluded from measurements of lattice parameters, WDXS and chemical analyses. The lattice parameter of EuPd₃B_x varies linearly with B content (x) with a distinct change of slope at x = 0.31. From Eu L_III XAS studies as well as from measurements of magnetic susceptibility it can be deduced that Eu atoms in EuPd₃ and in EuPd₃B_x (0 ≤ x ≤ 0.31) exhibit a 4f⁶ state, while for EuPd₃B_x (0.31 ≤ x ≤ 0.55) an intermediate valence state of (mixed 4f⁶ and 4f⁷) can be assumed. Our findings are discussed with respect to previously published studies [1,2].

[1] B. Darshan et al. Phys. Rev. B 30 (1984) 4031-4033.

[2] S. K. Dhar et al. Phys. Rev. B 29 (1984) 5953-5956.