THE MAGNETIC AND MAGNETOELASTIC PROPERTIES OF SURFACE CRYSTALLIZED IRON-BASED AMORPHOUS WIRE

The magnetic and magnetoelastic properties of surface crystallized iron-based amorphous wires have been investigated. The temperature and time conditions required to obtain the best magnetoelastic response by furnace annealing are defined from measurements of the field dependence of Young's modulus. The best magnetoelastic response is associated with an approximately linear field dependence of magnetization, anisotropy energy densities of about 100-300 J m-3 and coercivities below 10 A/m. The improved response is associated with a decrease in the anisotropy energy density and an increase in the average initial moment angle towards 90-degrees from the wire axis. This is supported by Mossbauer spectroscopy which reveals an increased fraction of magnetic moments perpendicular to the wire axis in the surface crystallized wire compared to the as-cast material. X-ray diffraction and etching experiments respectively confirm the presence of crystallization and the influence of surface crystallization as the controlling factor in the improvement of the magnetoelastic response. The magnitude of the stress imposed by surface crystallization for wires which have the best magnetoelastic response has been estimated to be 2-5 MPa and a domain structure is proposed which consists of oppositely magnetized domains in which the magnetic moments are oriented approximately circumferential.