Revealing structural distortion and dielectric relaxation in Ga_1-xSc_xFeO₃ (0≤x≤0.3)

Abstract

Polycrystalline samples of Ga_1-xSc_xFeO₃ (x=0, 0.1, 0.2, and 0.3) were prepared by solid state reaction method. The monophasic compounds were found to crystallize in the orthorhombic space group Pna21, confirmed from Rietveld refinement of the XRD patterns. The lattice constants were found to increase with increasing Sc content. Mössbauer measurements carried out at room temperature (RT) showed four paramagnetic doublets. Isomer shift values show that iron is in Fe³⁺ high spin state for all four Fe sites in all the compositions. Quadrupole splitting increases with Sc content which means that there is an increase in local structural distortion with Sc substitution. That Sc resides in the Ga2/Fe site was confirmed by Mössbauer spectroscopy. Low temperature Mössbauer study also shows a similar trend. Hyperfine magnetic field decreases with increasing Sc content. Sc substitution causes a reduction of magnetic ordering. The dielectric constant was found to decrease with increasing Sc content. The activation energies, obtained by the temperature dependence of dielectric relaxation as well as the conductivity, showed almost equal values around 0.3 eV.