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During the preparation process of the glass-covered magnetic aInorphous wires, axial, radial, and azimuthal internal stresses are induced, determining their magnetic properties. We have proposed a calculation method of the internal stresses induced during the solidification of the metal and during the cooling from the solidification temperature to room temperature due to the difference between the thermal expansion coefficients of metal and glass. For Fe77 QSi7 5B]5 glass-covered amorphous wires we found internal stresses of about 10 Pa. The values and distribution of these stresses depend on the radius of the metal and on the thickness of the glass cover. The stress distribution coupled with the specific high positive magnetostriction leads to an easy axes distribution associated with a magnetic domain structure consisting of a cylindrical inner core with axial magnetization and a cylindrical outer shell with radial magnetization.The inner core leads to the appearance of a large Barkhausen jump at low axial fields. We have calculated the ratio M"/M, (the reduced remanence) as being of about 0.75 -0.80. Magnetic measurements performed on samples prepared by us confirm the existence of the large Barkhausen jump but with a reduced remanence of about 0.95 that suggests the existence of a supplementary axial tensile stress. The dependence of the reduced remanence on external tensile stresses for wires covered by glass and after the glass removal confirms the existence of the supplementary stress whose value was estimated as being of the order of 10 Pa.

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Abstract:The magnetic characteristics of FINEMET type glass-coated nanowires and submicron wires are investigated by taking into account the structural evolution induced by specific annealing all the way from a fully amorphous state to a nanocrystalline structure. The differences between the magnetic properties of these ultrathin wires and those of the thicker glass-coated microwires and "conventional" wires with similar structures have been emphasized and explained phenomenologically. The domain wall propagation in these novel nanowires and submicron wires, featuring a combination between an amorphous and a crystalline structure, has also been studied, given the recent interest in the preparation and investigation of new materials suitable for the development of domain wall logic applications.

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