Enhancement of magnetic ordering temperature in iron substituted ytterbium manganate (YbMn1−xFexO3)

Oxides of the type YbMn1−xFexO3; x≤0.3 showing multiferroic behavior have been synthesized by the solid state route. These oxides crystallize in the hexagonal structure known for the parent YbMnO3 with the c/a ratio increasing with Fe substitution. The distortion of the MnO5 polyhedra (tbp) decreases and the Mn–O–Mn bonds in the a–b plane become shorter with Fe-substitution. Magnetic ordering is observed from the low temperature neutron diffraction study. The compounds were found to be antiferromagnetic and the ordering temperature TN increased from 82 K for pure YbMnO3 to 95 K for YbMn0.7Fe0.3O3. Variable temperature dielectric measurements (15–110 K) show an anomaly in the dielectric constant at temperatures close to the antiferromagnetic ordering temperature for all the compositions, showing a unique correlation between the magnetic and electric field. The increase in the ordering temperature in YbMn1−xFexO3 is explained on the basis of increase in covalence of Mn/Fe–O–Mn/Fe bonds (shorter) with iron substitution.