Inside The Electronic Structure Of The Sm3fe5o12 Garnet: A Mixed Ab Initio And Experimental Study

A combination of density functional theory (DFT) with experimental methods was used to study the electronic and crystal structure of Sm3Fe5O12 (SmIG), which was synthesized using a modified sol-gel method. Computational studies were performed within the generalized gradient approximation (GGA), with and without the Hubbard-U correction (DFT+U), to analyze the influence of the on-site repulsion on the band structure and the density of states (DOS) of SmIG, as well as the structural parameters. The calculations were contrasted with experimental results from x-ray diffraction (XRD) and UV-Vis spectra. A Rietveld refinement returned a lattice parameter of 12.5231(3) angstrom. Synthesis methods seem to have a substantial effect in the band gap of SmIG, as our experimental value of 2.26-2.27 eV differs from the 2.02 eV value previously reported for samples prepared using the traditional solid-state method, despite similar lattice parameters. The DFT-calculated lattice parameters were within 1% of the experimental value. Analytically calculated effective Hubbard-U values were 4.3092 eV for tetrahedral iron, and 6.0926 eV for octahedral iron. A model is proposed to calculate the band gap in Sm3Fe5O12, taking into account the structure's ferrimagnetism and energy level distribution. A direct transition between minority spin states was found, resulting in a calculated band gap of 2.27 eV, close to the aforementioned value from sol-gel synthesis.