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

First published as an Advance Article on the web 12th June 2003 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 Pb2FeReO6.1 from powder XRD data shows that the structure is cubic pyrochlore (a ~ 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