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The structure and magnetic properties of soft magnetic nanocrystalline composites crystallised from amorphous ribbons are reviewed. The Fe-Early Transition Metal-Boron (Nanoperm-type) nanostructures are discussed in details and compared to the Si containing (Finemet) alloys. The nanocrystallization process was studied by calorimetry; the spatial dimension, the composition and the relative fraction of the bcc and the residual amorphous phases were investigated by X-ray diffraction and Mössbauer spectroscopy. A small fraction of Fe atoms (about 4%) was found which cannot be assigned either to the residual amorphous or to the bcc phase. It is suggested that the magnetic anisotropy of the bcc phase is decreased due to the dissolved Zr and B impurities. The Curie point and Fe atomic moments in the residual amorphous tissue are determined and compared to that of a macrosized amorphous phase of similar composition. The observed deviations do not scale with the average characteristic size of the amorphous phase and thus cannot be explained in the framework of the existing models. Magnetic dipolar coupling and tensile stresses between the grains of the different phases are suggested for explaining the soft magnetic behaviour of the nanostructures. [ABSTRACT FROM AUTHOR]

Magnetic systems with a considerable amount of irregular interfaces were investigated by 57Fe Mössbauer spectroscopy. Chemically homogeneous ferromagnets around the percolation threshold composition of disappearing magnetism and chemically heterogeneous alloys prepared by nanocrystallization of amorphous alloys belong to this class of materials. Low temperature and high field measurements were performed on nanocrystalline FeZrBCu alloys, on ball milled Fe with nano size grains and on melt quenched amorphous Fe–Zr and Fe–Y alloys in order to clarify the origin of large high field susceptibility and to investigate the common features of the approach to magnetic saturation. Curie point determination of the residual amorphous phase in the nanocrystalline FeZrBCu alloys, results on the structure of the nanocrystalline b.c.c. phase and of the interfacial region will be reported. [ABSTRACT FROM AUTHOR]