A study of some properties for Li–Mn nanoparticles ferrite using positron annihilation lifetime technique

Nanoparticle samples of the composition Li_(0.5–0.5x)Mn_xFe_(2.5-0.5x)O₄, (x = 0, 0.25, 0.5 and 0.75) are prepared with a sol–gel auto combustion method. The nano grain size is decreased with increasing the manganese content. The analysis of PAL spectra indicated the existence of cluster defects. There are different correlations between the lifetime parameters with the manganese content. The relative intensity I₂ and the trapping rate ķ are increased for samples with x = 0.25 & 0.75, and are decreased for the sample with x = 0.5 relative to the pure nano Li-ferrite. The electrical resistivity takes the same behavior as the G.S. by increasing Mn content. The size of the domain walls is decreased with Mn content for mono-grain Li ferrite samples. - Highlights: • Lifetime values τ₂ confirm the existence of cluster defects at the domain walls. • The decrease of the domain walls thickness with increasing manganese content. • The decrease of the anisotropy energy and the exchange energy. • The decrease of the electrical resistivity is due to the decrease of the grain size. • It is a reverse behavior to the bulk ferrite