Sol-gel auto-combustion method was used to prepare fine Ni0,3Zn0,7Fe2O4 ferrite nanoparticles. The Ni-Zn ferrite has been calcinated at different temperatures from 900 ºC to 1300 ºC with step 100 ºC. Effects of sintering conditions on structure of Ni-Zn ferrite has been studied with Fourier transform infrared spectroscopy (FTIR) but particle nano-sizes were verified by atomic force microscopy (AFM). For all samples the FTIR spectra show two fundamental absorption bands, characteristics of metal vibrations at tetrahedral and octahedral sublattice states. Determined particle sizes for all composition were in nanometer range.