Magnetoelastic effects in amorphous wires and amorphous ribbons with nonmagnetic thin-film coatings

Abstract

We have measured the magnetomechanical coupling in amorphous 2605SC ribbons which have been coated by magnetron sputtering on one or both sides with copper films between 31 and 186 nm in thickness. Coating on one side produces an additional resonance mode which may be a coupling of an extensional and flexural mode. Coating on both sides greatly increases the anisotropy and reduces the coupling factor. Analysis indicates that these effects are due to stresses imposed by the coating on the ribbon and can be ameliorated by control of deposition parameters. In transverse-field annealed amorphous Fe77.5B15Si7.5 wire material we find a lower coercive force and lower values of applied fields required for saturation than in our ribbon investigations. This is probably due to a lower surface-to-volume ratio for the amorphous wire, i.e., surface defects play a lesser role in the wire geometry. We find a different magnetization process. Values of magnetomechanical coupling approach ribbon values. Saturation values of magnetostriction are equivalent. Values of the transverse anisotropy in the wire material are lower than what we have previously obtained in our ribbon material. We conclude that the amorphous wire will be a good sensor material.