Cation-ordered Pb2-xBixMnO4 solid solutions with magnetic frustration

Abstract

A new solid solution of composition Pb2-xBixMnO4 (0 ≤ x ≤ 0.3) has been synthesised by solid-state reaction at 730 °C. The crystal structures have been investigated using X-ray and neutron diffraction. The replacement of Pb2+ by Bi3+ ions induces reduction of Mn4+ to Mn3+ with an increase in lattice volume. The Bi3+ ions preferentially occupy the five-coordinated rather than four-coordinated Pb sites. Magnetic measurements and neutron diffraction reveal antiferromagnetic transitions in these materials. A clear increase in magnetic frustration and suppression of magnetic order is evidenced for Pb1.7Bi0.3MnO4 through the long-range order of a small ~1.0 µB AFM moment below TN.