Structural, Electronic, and Magnetic Properties of Gd-Substituted Bi2Fe4O9 Multiferroic: A Combined Experimental and DFT Approach

We present the structural, electronic, and magnetic properties of Gd3+ substituted Bi2Fe4O9 (BFO) via experimental analysis as well as density functional theory (DFT). Rietveld refined X-ray diffraction data shows phase purity of the samples having orthorhombic phase with space group: "Pbam." Gd3+ ions substitution at Bi3+-site is confirmed by the shift in peaks ((002) and (220)) at higher 2 theta angles as well as the reduction in lattice parameters. The PBE+U calculations predict a band gap of 1.76 eV (BFO) and 1.6 eV (Gd substituted BFO) which is in close agreement with the experimental values. This reduction in band gap due to Gd3+ substitution enhances conduction in substituted samples. The calculated density of states illustrates considerable hybridization between Fe-3d and O-2p states with substantial overlap among the Bi-6p and O-2p states. Incorporating Gd3+ ions further introduces additional exchange interactions between Gd-Fe-t and Gd-Fe-o, thus leading to enhanced magnetization as well as an increase in antiferromagnetic transition temperature (T-N). This characteristic feature is supported by temperature-dependent magnetic susceptibility (chi) and d chi/dT plots. Hence, our experimental and theoretical findings suggest that BFO and its substituted samples are potential multiferroic materials for various device applications.