The temperature and concentration dependence of the hyperfine field distribution in the Mössbauer spectra of Fe nuclei in FeZr amorphous alloys are studied. The relation between the low-field component and the Invar anomaly is also investigated. The nonmagnetic densities of electronic states of the model clusters Fe14 and Fe14Zr and the influence of cluster deformations simulating the interatomic distance fluctuations are calculated. The results show that the Fe atom with unstable magnetic moment causes the magneto-volume anomaly. The Fe atoms with next-nearest-neighbour Zr atoms possess unstable moments. Some Fe atoms among nearest neighbours also show a decrease of the moments with increasing temperature. These atoms have smaller interatomic distances as confirmed by the density of states calculations. [Russian Text Ignore]