Magnetic and electronic properties of LiFe1-xGaxCr4O8 double spinel by Ga doping

In this work, the solid solution of the double spinel LiFe 1-x Ga x Cr 4 O 8 was synthesized and characterized by X-ray diffraction, magnetic susceptibility measurements, UV–Vis–NIR spectroscopy, and X-ray photoelectron spectroscopy (XPS). Rietveld refinements show that the crystal structure is cubic with space group F 4 ‾ 3m (No. 216), which is maintained as Fe is gradually substituted by Ga. The lattice parameter a and unit cell volume V decrease consistently due to the smaller ionic radius of Ga compared to Fe. Magnetic susceptibility data indicate that increasing Ga content reduces ferrimagnetic behavior while enhancing the antiferromagnetic component. From Density Functional Theory (DFT) calculations and using Hubbard-corrected Local Spin Density Approximation (LSDA + U) we observe that LiGaCr 4 O 8 has a direct electronic band gap (E g ) of 1.73 eV at the Γ point. Additionally, UV–Vis–NIR spectroscopy reveals an increasing of the direct optical band gap (E g ) with increasing Ga concentration, from 1.43 eV at x = 0.25–1.54 eV at x = 1.00. XPS analysis of Li 1s , Fe 3p , Ga 3d , Cr 3p , and O 1s core levels, together with the valence band (VB), reveals through detailed spectral deconvolution that the oxidation states of Li 1+ , Fe 3+ , Ga 3+ , and Cr 3+ remain constant throughout the solid solution. • Ga doping reduces lattice parameter and volume while preserving crystal symmetry. • Ga substitution reduces ferrimagnetism and enhances antiferromagnetic interactions. • The optical band gap increases with Ga substitution, confirmed by UV–Vis. • DFT confirms a direct band gap of 1.73 eV and antiferromagnetic behavior. • XPS confirms stable cation valences and higher valence band intensity near 0 eV.