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Figure 7. Maximum magnetic anisotropies versus current annealing intensity induced in Fe73 5CujNb3Si15 5B7 samples. Reprinted with permission from [76], C. Miguel et al., Phys. Status SolidiA 194, 291 (2002). © 2002, Wiley-VCH.

anisotropy decreases with the current density down to minimum value. Such minimum is observed again at around 45 A/mm2. For current densities higher than that of the maximum, induced anisotropy monotonically decreases with current annealing density.

Studies on the stress-induced anisotropy [68-76] indicate that resembling behaviors as those in metallic glasses also can be found in Finemet type nanocrystalline magnets. Although the occurrence of this effect has been well confirmed, nevertheless, its origin seems to be not entirely understage at present. Herzer proposed [70] an explanation, claiming that this anisotropy is of a magnetoelastic nature and is created in the nanocrystallites a-Fe(Si) grains due to tensile back stresses exerted by the anelastically deformed residual amorphous matrix. The above conclusion seems to be highly probable because of a strong correlation between the stress-induced anisotropy and the magnetostriction of the nanocrystallites found by Herzer [70]. However, Hofmann and Kronmuller [72] and Lachowicz et al. [73] suggested an alternative explanation of the origin of the considered anisotropy. They adapted the Neel's calculations of atomic pair directional ordering proposed by Neel [77] to the conditions of the investigated material, obtaining a theoretical value of the energy density of the stress-induced anisotropy of the same order of magnitude as that observed experimentally. Consequently, besides the magne-toelastic interactions within the nanocrystallites suggested by Herzer, the directional pair ordering mechanism in a-Fe(Si) grains is also a very probable origin of the stress-induced anisotropy in Finemet-type material.

The occurrence of dipolar and deteriorated exchange intergrain interaction also should be considered to explain the origin of the stress-induced anisotropy in the nano-crystalline alloys [19, 49]. This leads to a more realistic situation than the simple anisotropy averaging, since those features are involved in the accomplishment of a nanocrystallization process. In this way, the procedure to obtain the weighted average anisotropy nicely proposed by

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