X-ray diffraction and IR spectroscopy have been used to study the mixed ferrite Lio.s+o.s,Ge,FeZ.s_l.~O, (where x=0.0, 0.2-0.5). The X-ray diffraction data established that the prepared samples were homogeneous and that spine1 structure was formed. The lattice parameter for each composition was calculated; the lattice parameter of the sample with x=0.0 was 0.832 nm, and that for x=0.2-0.5 had a constant value of ~0.828 nm. IR spectra were recorded in the range 200 to 1200 cm- I. Three main bands were observed. The band at ~600 cm-’ (Ye) and the band at ~400 cm-’ (y) were assigned to the tetrahedral and the octahedral complexes, respectively. A small band (v3) at ~350 cm-’ indicated the presence of octahedral divalent metal-oxygen in the complexes. When Ge content was introduced, a shoulder band appeared at 790 cm-‘. This band can be related to the stretching vibrational modes of GeO, tetrahedra.