Exploring the impact of La and Co doping and co-doping on the structural, microstructural, magnetic, and optical properties of α-Fe2O3 films via spray pyrolysis

Abstract

α-Fe₂O₃, (Fe₇₀Co₃₀)₂O₃, (Fe₇₀La₃₀)₂O₃, (Fe₇₀Co₂₀La₁₀)₂O₃, and (Fe₇₀La₂₀Co₁₀)₂O₃ thin films were synthesized by the spray pyrolysis procedure on glass substrates. The effect of cobalt and lanthanum doping and co-doping on the structural, microstructural, magnetic, and optical properties was investigated using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and UV-visible spectroscopy. The XRD analysis revealed the formation of the hematite-type structure for all samples with slight variations in the lattice parameters in the range of a = 5.0212−5.0358 Å and c = 13.7203−13.7416 Å. The crystallite size decreases to 40–58 nm with La³⁺ and Co²⁺ incorporation into the α-Fe₂O₃ crystal structure. Co and La doping and co-doping influence the surface morphology of the films. FTIR analysis confirmed the retention of Fe–O and O–Fe–O vibrations of the hematite matrix. Room temperature hysteresis loops revealed a paramagnetic behavior for the La-doped Fe₂O₃ and a ferromagnetic state with enhanced saturation magnetization for Co-doped and (La, Co) co-doped films. Optical transmittance spectra indicated high transparency, increasing the energy bandgap from 2.22 eV to 2.43 eV. These results highlight the potential of La and Co co-doped hematite thin films for optoelectronic and spintronic applications.