Small-Angle Neutron Scattering Investigations of Nanoscaled Microstructures

The formation and stability of nanoscaled microstructures upon annealing of two amorphous systems have been investigated by small-angle neutron scattering (SANS). The bulk amorphous alloy Zr₄₁Be_22.5Ti₁₄Cu_12.5Ni₁₀ decomposes into two supercooled liquid phases upon annealing above the glass temperature. Dynamic scaling has been demonstrated for this phase-separation process. Crystallization is significantly slowed down by the two-phase nanoscaled microstructure formed upon decomposition. The temperature and magnetic field dependence of the anisotropic SANS scattering profiles in Fe_73.5Si_15.5B₇M₄ (M = Nb, W, Cu) alloys revealed superparamagnetic behaviour of Fe₃Si nanocrystals which are decoupled from the amorphous ferromagnetic matrix. An Nb-enriched nonmagnetic layer formed around the Fe₃Si crystals during diffusion-limited growth prevents magnetic exchange interactions and the coarsening of the nanocrystals.