On the Effect of Magnetic Pulsed Treatment on the Surface Structure and Magnetic Properties of Ribbon Amorphous Fe(Ni,Cu)(SiB) Alloys

We explore the specific features of the surface state that determine the domain structure, magnetic properties and magnetic loss upon magnetization reversal of ribbon amorphous Fe(Ni,Cu)(SiB) alloys obtained by ultrafast cooling by melt sputtered onto a rotating drum. We use scanning electron microscopy, atomic-force microscopy, and magnetic-force microscopy and measurements of the magnetic characteristics before and after treatment by pulses of a weak magnetic field (10-100 kA/m) of low frequency (10-20 Hz). Both foil surfaces are studied. The surfaces of the samples adjacent to the copper drum had an inhomogeneous structure, typical of all rapidly hardened samples. The other sides of the foils are smoother, which make them look shiny. Atomic-force microscopy shows no changes in the surface structure of the foils after their magnetic-pulse processing. Changes are detected in the images of the shiny side of the samples, obtained by magnetic-force microscopy. No domain structure is observed in the samples before magnetic-pulse processing. After magnetic-pulse treatment, stripe domains with a width of 0.6-0.8 nm and closure domains with a width of 1.0-1.6 nm are found at structural defects, and a weak magnetic contrast as large and small domains with a shape close to triangular is detected in some areas of the surface. The magnetization-reversal loss is largely related to the loss caused by eddy currents and is affected by the domain width (about 1.5 nm), which depends only slightly on the modes of magnetic-pulse processing. The results can be used to refine the procedure for relieving stress arising during the manufacturing of amorphous ribbons.