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The perovskites PbFeO2F and 0.5PbFeO2F-0.5PbTiO3 were synthesized at high temperatures (1000°C) and high pressures (4 – 6 GPa). The crystal and magnetic structures were determined using powder neutron diffraction. Quenched PbFeO2F has the cubic perovskite-type, Pm3m, structure in which the Pb ion shifts from ideal A-site along the directions, which is in good accordance with a previous report. The magnetic structure is antiferromagnetic G-type with propagation vector k = (1/2 1/2 1/2) and an Fe3+ ordered moment of 3.83 μB at 283K. The Néel temperature is 655(5) K. Annealed PbFeO2F has a tetragonal perovskite-type structure at room temperature and transforms reversibly from tetragonal to cubic at approximately 470 K. A superlattice with dimensions a × a × 5c is observed both in electron and x-ray diffraction. The solid solution 0.5PbFeO2F-0.5PbTiO3 belongs to the non-centrosymmetric space group P4mm. The magnetic structure is G-type antiferromagnetic and shows a weak ferromagnetic moment at 4 K. Consequently, 0.5PbFeO2F-0.5PbTiO3 is simultaneously ferroelectric and a weak ferromagnet at low temperature. The Néel temperature is 450 K but the temperature dependence of the ordered Fe moment is anomalous.

Bulk physical properties of layered pnictide-oxides, Na2Ti2Pn2O (Pn = As, Sb) have been characterized. Both As and Sb compounds exhibit anomalous transitions in temperature dependent magnetic susceptibility and electrical resistivity. The powder neutron diffraction data show no superlattice reflections indicative of long-range order. The origin of the physical property anomalies and structure-property relationship between As and Sb compounds are described in terms of a charge-density-wave/spin-density-wave mechanism.