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

TL;DR

This study synthesizes new pyrochlore oxides Ln2ScNbO7 with various lanthanides, analyzes their structure, and investigates their magnetic properties, revealing geometric frustration and unique magnetic behavior in Eu-containing phases.

Contribution

First synthesis and structural analysis of Ln2ScNbO7 pyrochlores with multiple lanthanides, including magnetic property characterization and discussion of geometric frustration effects.

Findings

All compounds crystallize in cubic pyrochlore structure.

Europium phase exhibits constant magnetic susceptibility below 50 K.

No magnetic ordering observed down to 2 K.

Abstract

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.