Synthesis and structure of new pyrochlore-type oxides Ln2ScNbO7 (Ln = Pr, Nd, Eu, Gd, Dy)

Siwar Zouari (1) , Rafik Ballou (2) , Abdelwaheb Cheikh-Rouhou (1) , Pierre Strobel (3)

1 Laboratoire de Physique des Matériaux
2 NEEL - MagSup - Magnétisme et Supraconductivité
3 NEEL - MRS - Matériaux, Rayonnements, Structure

We report the synthesis and structural study of mixed oxides in the Ln2ScNbO7 series. New phases with Ln = Pr, Eu, Gd and Dy are obtained. All crystallize in the cubic pyrochlore structure type, space group F-d3m, with no Sc-Nb ordering on the B-site. The structures are determined by Rietveld refinement. The evolution of cell parameters, interatomic distances and angles as a function of lanthanide cation size is discussed. Magnetic measurements show the absence of ordering down to 2 K, in agreement with the presence of strong geometric frustration in the lanthanide sublattice. The europium phase shows a peculiar magnetic behaviour; its magnetic susceptibility becomes constant below ca 50 K. This feature confirms the behaviour observed previously on Eu2Ti2O7 and is ascribed to crystal field effects.

Mots clés: ternary oxides; pyrochlores; crystal structure; magnetic materials

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Siwar Zouari, Rafik Ballou, Abdelwaheb Cheikh-Rouhou, Pierre Strobel. Synthesis and structure of new pyrochlore-type oxides Ln2ScNbO7 (Ln = Pr, Nd, Eu, Gd, Dy). Materials Letters, 2008, 62, pp.3767. ⟨10.1016/j.matlet.2008.04.060⟩. ⟨hal-00347195⟩