Magnetization measurements in the temperature range 1.5-300 K have been made on two series of samples of nanocrystalline ferromagnets: Fe₆₀Co₃₀Zr₁₀ and Fe_73.5CuNb₃Si_13.5B₉. It was found that at low temperatures magnetization decreases in accordance with the Heisenberg-model prediction for both series of samples. The coefficients B and C were obtained by fitting M_s(T) to two terms, T^3/2 and T^5/2, from the Bloch law. It is shown that for both series of samples the B and C coefficients are larger in the amorphous state than in the nanocrystalline state; larger values of spin-wave stiffness constants D were obtained in nanocrystalline FeCoZr samples with grain size d<40 nm than in the amorphous state; with increasing grain size a much larger value for D was observed for nanocrystalline FeCoZr with a grain size of 140 nm. The results present a reasonable agreement with predictions for nanocrystalline materials with two or three different magnetic phases.