Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe_1−xSc_x)_2∕3W_1∕3O₃ solid solutions

Abstract: Ceramic samples of the multiferroic perovskite Pb(Fe_1−xSc_x)_2∕3W_1∕3O₃ with 0 ≤ x ≤ 0.4 have been synthesized using a conventional solid-state reaction method, and investigated experimentally and theoretically using first-principle calculations. Rietveld analyses of joint synchrotron X-ray and neutron diffraction patterns show the formation of a pure crystalline phase with cubic (Fm3^̅m) structure with partial ordering in the B-sites. The replacement of Fe by Sc leads to the increase of the cation order between the B′ and B′′ sites. As the non-magnetic Sc³⁺ ions replace the magnetic Fe³⁺ cations, the antiferromagnetic state of PbFe_2∕3W_1∕3O₃ is turned into a ferrimagnetic state reflecting the different magnitude of the magnetic moments on the B′ and B′′ sites. The materials remain ferroelectric relaxors with increasing Sc content. Results from experiments on annealed and quenched samples show that the cooling rate after high temperature annealing controls the degree of cationic order in Pb(Fe_1−xSc_x)_2∕3W_1∕3O₃ and possibly also in the undoped PbFe_2∕3W_1∕3O₃. Graphical abstract: [Figure not available: see fulltext.].