A STM study of the microstructure of amorphous and nanocrystalline Fe-Zr-B-Cu ribbons

The surface microstructures of amorphous and nanocrystallized melt-spun Fe₈₆Zr₇B₆Cu ribbons have been studied by means of scanning tunneling microscopy. The amorphous sample has a smooth, almostfeatureless surface. On the other hand, the nanocrystallized sample consists of a homogeneous distribution of ellipsoidal clusters (≈ 300 nm × 150 nm) aligned along the casting direction and composed of randomly oriented nanocrystallites of about 10 nm in diameter consistent with transmission electron microscopic observations. The nanocrystallites themselves have a smooth morphology, rather than a grainy surface. The smaller size of the nanocrystallites in comparison with the ferromagnetic exchange length (about 50 nm) gives rise to the improved soft magnetic properties in these nanocrystallized ribbons.