Magneto-resistance, stress effects, and a self-similar expansion model for the magnetization processes in amprphous wires
The outer shell magnetization process was investigated from the point of view of its effects on longitudinal and transverse magnetoresistance (MR), magnetization, and domain structure observations as well as their stress effects for a Fe/sub 77.5/Si/sub 7.5/B/sub 15/ amorphous wire with a diameter of 125 mu m prepared by rapid quenching in rotating water. The unusual behavior of the initial negative slope observed in the longitudinal MR is explained in terms of a realistic domain structure. A self-similar expansion model is proposed to explain the dynamical response of such a structure under applied fields and/or tensile stresses. It is suggested that the zig-zag domains of the outer shell are stabilized by a square closure domain which expands uniformly while maintaining a self-similar shape up to a threshold field of about 20 Oe and then deforms towards the saturation magnetization. However, this domain structure was destroyed or much deformed by a tensile stress along the wire axis of about 170 MPa in the sample. Such a critical stress depends on the diameter, quenching conditions, alloy composition, etc. This behavior and stabilization of the zig-zag domain by the closure domains give a novel mechanism for the magnetization processes which follow the re-entrant reversal, and are thus useful for the understanding of re-entrant reversal phenomena themselves. >
Scattering Centers for Magnetoelastic Waves in Amorphous Wires
Scattered magnetoelastic waves were observed in as-quenched and annealed amorphous Fe-Si-B wires in order to clarify the nature of the scattering centers. Neither a magnetic field nor tensile stress applied to the wire changed the waveform of the scattered waves. According to observations of scattered waves in annealed wire, the annealing process has no significant effect on the properties of the scattering centers. These experimental results indicate that the scattering centers are caused by fluctuations of some elastic properties along the wire which are introduced by the quenching process, and that they are spaced a few millimeters apart on average.
Magnetization processes in the narrow domain structures of amorphous ferromagnetic alloys
Abstract The magnetization processes within the narrow domain laminae of amorphous ferromagnetic alloys have been investigated by means of the magneto-optical Kerr effect. Changes of the domain width of the closure domains by a magnetic field applied perpendicular to the laminae have been determined for the alloys Fe 80 B 20 and Fe 40 Ni 40 P 14 B 6 . These results are compared with theoretical calculations, assuming that wall displacements within the closure domains and rotations of the magnetization in the bulk domains take place simultaneously and a stray field free domain structure is developed. It turned out, that the closure domain structure on the surface of the sample vanishes at the same magnetic field where magnetic saturation is approached.