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Figure 5. Current density dependence of the saturation magnetisation of samples previously treated at 40 A/mm2 with 0, 0.5, 1, 2, 5, 60, 120, 300, and 720 min. Reprinted with permission from [62], J. González, J. Mater. Res. 18, 1038 (2003). © 2003, Materials Research Society.

Figure 6. Variations of coercive field with current density of samples previously treated at 40 A/mm2 with 0, 0.5, 1, 2, 5, 60, 120, 300, and 720 min. Reprinted with permission from [62], J. González, J. Mater. Res. 18, 1035 (2003). © 2003, Materials Research Society.

magnetic alloys from the application viewpoint. On the other hand, the intergranular residual amorphous phase plays an important role. The presence of the residual amorphous phase is essential to maintaining the metastable thermo-dynamical equilibrium of the nanostructure. This behavior should be understood, taking into account the compositional change of the amorphous matrix (with progressive lost of Si and Fe with the annealing time), which can significantly change the Curie point of this phase. Unavoidable mixing of atoms at the interface nanocrystal-amorphous gives rise to the formation of thin layers of alloys with unknown compositions. It has been proposed that the exchange penetration is likely to be the main cause of the Curie temperature enhancement of the matrix, but with contributions from a magnetostatic interaction as well as compositional sharp gradients of the interface. Unfortunately, the lack of knowledge about the nature of this interface opens an interesting question related to the coupling between two phases with a large interface area as is the case of these soft magnetic nano-crystalline Fe-base alloys.

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