Magneto-mechanical rotation of magnetostrictive amorphous wires

The mechanical rotation of both positive (FeSiB) and negative (CoSiB) magnetostrictive rapidly quenched amorphous wires, when submitted to an alternating axial magnetic field (Hac) with a frequency of a few kHz, has been investigated. Hac was varied from a few A/m to around 21 kA/m and a laser-based method was implemented to accurately determine the wire rotation frequencies. The appearance of such effect was found to be directly related with both the magnetostrictive nature of these materials and the diameter of the inner tube of the alternating current coil, φ, in which the wires were placed. A dynamical equilibrium of the effect of rotation was only reached for small values of φ. Different frictional arrangements yielded modifications of the spectrum obtained on plotting exciting frequency versus wire rotation frequency (typically several tens of Hz). When rotation started, a directionally controlled axial direct current magnetic field was applied, which eventually made the wires stop rotating. Accordi...