Magneto-mechanical rotation of magnetostrictive amorphous wires

The mechanical rotation of both positive (FeSiB) and negative (CoSiB) magne tostrictive rapidly quenched amorphous wires, when submitted to an alternat ing axial magnetic field (H-ac) with a frequency of a few kHz, has been inv estigated. H-ac was varied from a few A/m to around 21 kA/m and a laser-bas ed method was implemented to accurately determine the wire rotation frequen cies. The appearance of such effect was found to be directly related with b oth the magnetostrictive nature of these materials and the diameter of the inner tube of the alternating current coil, phi, in which the wires were pl aced. A dynamical equilibrium of the effect of rotation was only reached fo r small values of phi. Different frictional arrangements yielded modificati ons of the spectrum obtained on plotting exciting frequency versus wire rot ation frequency (typically several tens of Hz). When rotation started, a di rectionally controlled axial direct current magnetic field was applied, whi ch eventually made the wires stop rotating. According to our experimental r esults and observations the initial torque, which yields the mechanical rot ation of these wires, would be originated on adding the force asserted by a magnetoelastic wave and the friction force. (C) 1999 American Institute of Physics. [S0003-6951(99)04240-0].