Permeability and magnetic interactions in Co2+ substituted Li0.5Fe2.5O4 alloys

•Co2+ substituted lithium ferrite.•Structure changes from order to disorder.•Coercivity increased with Co2+ substitution.•Blocking temperature increased whereas Curie temperature decreased with Co2+ substitution.

A series of spinel ferrites, Li0.5Co1.5xFe2.5−xO4, with x = 0.0, 0.25, 0.50, 0.75 and 1.0 were successfully synthesized by sol–gel auto combustion method, aiming to study the relationship between structural and magnetic interactions related to the concentration of the substituted cobalt cations. X-ray diffraction measurements were employed for analyzing the structure, lattice parameter, density, porosity and crystallite size of the prepared samples. Samples have the cubic spinel structure with a small amount of α-Fe2O3 and γ-Fe2O3. As the Co2+ ions increases, hematite and maghemite phases disappear and the crystals form the single phase spinel structure with the cation ordering on octahedral sites. Lattice constant (a) increases from 8.331 to 8.423 Å with increase in Co2+ substitution. Particle size estimated from the transmission electron microscopy images, and is ranging from 12 to 23 nm. Infrared spectroscopy measurements were carried out to study the band position and structure of the sample. Saturation magnetization decreased linearly from 41.21 to 28.84 A m2/kg with an increase in Co2+ content. It was found that coercivity increased with the Co2+ substitution from 8678 to 75636 A/m. The samples were zero field cooled to 100 K. Typical blocking effects were observed below about 253 K. Curie temperature (TC) were obtained from AC susceptibility and permeability measurements shows the decreasing trend with Co2+ substitution, indicating the weakening in A–B interactions. Permeability decreased with the increase in Co2+ substitution due to the combine effect of magnetization and magnetocrystalline anisotropy.

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