Mössbauer analysis, structural parameter studies and magnetic properties of LiCoxFe5-xO8 (x= 0, 0.025, 0.05, 0.075, 0.1) nanoparticles

Abstract

We report on detailed structural parameter analysis, Mössbauer spectra and magnetic properties of LiCoxFe5-xO8 (x = 0, 0.025, 0.05, 0.075, 0.1) nanoparticles prepared by sol-gel method. Prepared LiCoxFe5-xO8 nanoparticles crystalizes in inverse spinel structure with the crystallite size ranging from 23.7 to 29.8 nm. Hopping length, radii of tetrahedral and octahedral sites (rA and rB), tetrahedral bond length (dAx), octahedral bond lengths (dBx), tetrahedral and octahedral shared edges (dAxE, dBxE), unshared octahedral edges (dBxEU) values and oxygen positional parameter (u) are seen to increase with increasing Co concentration. Chemical state of all the elements are confirmed by X-ray photoelectron spectroscopy technique. The hyperfine field, isomer shift, quadrupole shift and line width parameters calculated from the Mössbauer spectra confirms the Co2+ substitution in LiFe5O8. The saturation magnetization value decreases from 59.2 to 54.1 emu/g with increasing Co concentration, which is examined by three sublattice model derived by Yafet and Kittel (Y-K model). Y-K angles increases with Co concentration from 16.46 to 19.98°. Curie temperature of LiFe5O8 decreases from 865 K to 858 K with increasing Co concentration to x = 0.1.