Pb₂FeReO₆: new defect pyrochlore oxide with a geometrically frustrated Fe/Re sublattice

Abstract

Nominal Pb₂FeReO₆ adopts a defect pyrochlore structure at ambient pressure unlike the other A₂FeReO₆ (A = Ca, Sr, Ba). Rietveld refinement of the crystal structure of one of the compositions Pb₂FeReO_6.1 from powder XRD data shows that the structure is cubic pyrochlore (α = 10.382 Å ; space group: Fd3m) where oxygen vacancies occur at O2 (8b) sites. The divergence between the ZFC and FC magnetic susceptibility data and the non-Arrhenius resistivity behaviour of Pb₂FeReO₆ compositions are characteristic of the underlying geometrically frustrated Fe/Re cation sublattice in the pyrochlore structure.