EN
Detailed magnetization measurements were performed on amorphous Fe_{1-x}Zr_{x} alloys with 0.14 ≤ x ≤ 0.48 at temperatures ranging from 4.2 K to the Curie temperature in external magnetic field up to 5 T. An analysis of the experimental data reveals that' the fluctuations of the exchange integral resulting from the structural disorder give important contribution to the thermal demagnetization and high-field susceptibility of Fe-rich alloys. For Zr-rich alloys the effect of fluctuations of the exchange integral is negligible and thermal demagnetization is described in terms of spin-wave excitations. No Stoner single-particle excitations were observed for alloys with x > 0.14.