Investigation of structural, morphological, optical, and magnetic properties of Sm-doped LaFeO3 nanopowders prepared by sol–gel method

Abstract

Pure orthorhombic phase of La1−xSmxFeO3 (x = 0, 0.1, 0.2, and 0.3) nanoparticles can be obtained by sol–gel method after calcination at 800 °C for 3 h in air. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge spectroscopy, ultraviolet-visible spectroscopy, and vibrating sample magnetometry were used to study the crystal structure, morphology, oxidation state, functional group, optical, and magnetic properties of samples. Pure orthorhombic phase of perovskite structure is confirmed by X-ray diffraction results. Decreasing lattice parameters, crystallite sizes, and cell volumes with increasing microstrains indicate structure distortion due to the substitution of Sm ions with small ionic radius on the La sites in the orthorhombic structure. Scanning electron microscopy and transmission electron microscopy images show a homogeneous distribution of almost spherical nanoparticles with decreasing average particle sizes ranging from 56.48 ± 3.22 to 23.21 ± 4.40 nm for samples of high Sm content. Fourier transform infrared spectroscopy spectra confirm the Fe–O stretching mode in octahedral FeO6 unit of a perovskite structure. X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy results indicate the oxidation states +3 of La and Fe ions. The optical band gaps are found to decrease from 2.218 to 1.880 eV with increasing Sm content. vibrating sample magnetometry results show the antiferromagnetic behavior of undoped sample and ferromagnetic behavior for doped samples, affecting by structure distortion and particle size reduction. Interestingly, the coercive field is significantly enhanced from 95.07 Oe (x = 0.1) to 13,062.79 Oe (x = 0.3). Curie temperature (T c) is suggested to be above 400 K. The magnetization curves of La1-xSmxFeO3 (x = 0.0, 0.1, 0.2, and 0.3) nanoparticles prepared by the sol-gel method with the inset show the comparing coercive forces (Hc) of the present work and the previous works, La0.7M0.3FeO3 (M = Al and Ga). Sm-doped LaFeO3 nanoparticles can exhibit ferromagnetic behavior with the significant enhancement of Hc from 95.07 to 13,062.79 Oe.