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Having determined the deviations of ellipsometrical parameters for light reflected from the ribbon surface as a function of its orientation in the ribbon plane, the level of internal strain changes in the subsurface layer of Fe-based (Fe75Ni4Mo3Si2B16 and Fe70Cr15B15 ) amorphous metal alloys has been analyzed. Optical measurements were carried out for as-casted ribbons at 12 (Fe75Ni4Mo3Si2B16) and 4 (Fe70Cr15B15 ) orientations of the ribbon longitudinal axis relatively to the plane of light incidence. For each orientation phase shift Δ between p- and s-components of the polarization vector and an azimuth Ψ of the restored linear polarization have been obtained using a LEF-3M reflectometer-goniometer. From the angular dependence Δ(φ) (φ is angle of light incidence), the principal angle φ0 of light incidence was determined. Then, by rotating the sample around a normal to its surface within 360°, the polar diagrams (so-called indicatrices of ellipsometric parameters on rotation azimuth α) have been determined. The noncircular form of the polar diagram indicates a high sensitivity to internal stress variations arising during ribbon preparation. For Fe70Cr15B15 ribbons the long-time irradiation even by comparatively small fluencies of neutrons, causes structural relaxation and essentially influences on optical properties in the IR. It was determined that in the IR a real part of the complex dielectric function ε1>0 at any values φ angle of light incidence and α (azimuthal orientation of the ribbon longitudinal axis with respect to the light incidence plane).
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