Nickel ferrite has been synthesized by microwave and auto combustion method. Crystal structure has been confirmed by XRD. The FT-IR spectra of synthesized ferrites showed two absorption bands (ν1 and ν2) in the range 400–600 cm–1 belonging to tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. From Fourier transform infrared spectroscopy, stiffness constants (for isotropic material, C11=C12), longitudinal elastic wave (Vl), transverse elastic wave
(Vt), mean elastic velocity (VMean), rigidity modulus (G), Poisson’s ratio(s) and Young’s modulus (E) of ferrites has been computed and compared by these two methods.