Mossbauer studies of structure relaxations near nanocrystallization region in amorphous Fe90Zr7B3 alloy

Transmission Mossbauer spectra and high-resolution electron microscopy investigations for amorphous Fe90Zr7B3 alloy in the as-quenched state and after annealing in vacuum at temperatures 673, 723 and 743 K have been performed. In the as-quenched state the microstructure reveals the presence of medium range order BCC- or FCC-like structure regions 1-3 nm in size which grow during annealing at 673 K being the nuclei of grains of alpha-Fe phase. After annealing at 723 K for 1 h, the grains 16 nm in diameter and with the average distance of 110 nm between them are embedded in the paramagnetic amorphous matrix. This distance is large enough to prevent magnetic interaction between the grains, and superparamagnetic behavior is observed. After longer annealing at 723 K and at 743 K, the Mossbauer spectra show a crystalline component of the alpha-Fe phase with the inhomogeneous amorphous matrix consisting of para- and ferromagnetic phases. The hyperfine induction of the crystalline phase slightly increases with time and annealing temperature which is ascribed to the faster diffusion of atoms.