Ferromagnetic and antiferromagnetic orders in low dimensional PbBiFe1-xMxO4 (M = Mn and Co) solid solutions

Abstract

A new solid solution of composition PbBiFe1-xMxO4 (M ​= ​Mn and Co, 0 ​≤ ​x ​≤ ​0.15–0.2) with low structural dimensions has been synthesized by solid-state reaction at 873–923 ​K. The crystal structures have been investigated using X-ray and neutron diffraction. The presence of Co2+/Co3+ on the Fe3+ sites and oxygen vacancies in PbBiFe1-xCoxO4 is revealed by its unusual volume increase and TGA, while the volume contraction of PbBiFe1-xMnxO4 indicates the substitution of Mn4+/Mn3+ on the Fe3+ sites. This leads to unexpected greater and smaller metal-metal distances inside the chains for the Co and Mn case, respectively, compared with the undoped materials. All the PbBiFe1-xMxO4 materials display long-range antiferromagnetic order but are suppressed by cationic substitution, as evidenced by a decrease in TN. Additional intrinsic short-range ferro- (or ferri-) magnetic transitions in the Co-doped materials are evidenced by magnetic hysteresis and frequency-dependent χ’ peak around TF. The introduction of ferromagnetic intrachain clusters in PbBiFe1-xCoxO4 is rationalized through a competitive mechanism between direct AFM exchange interaction and 90°- type FM superexchange interactions, which provided insights to tune the magnetic properties and design low dimensional functional materials.