AC magnetic field induced rotation in levitating magnetostrictive wire

Summary form only given. Magnetostrictive wires can exhibit spontaneous mechanical rotations (range of tens of Hz) when subjected to alternating magnetic field (order of kHz) under suitable conditions. This surprising effect has been reported in wires with diameter ranging from 0.1 to 1 mm, several cm long, irrespective of the alloy composition and structural nature (amorphous or microcrystalline), but always with large enough magnetostriction. According to recent experiments, the origin of the effect is connected to the generation of magnetoelastic standing wave resulting in mechanical vibrations that transform into effective coherent rotation. This is further supported by the fact that the rotation maybe induced by mechanical vibrations excited by a membrane loudspeaker. In the present work, latest results are reported in 3 mm diameter FeNi polycrystalline wires including field induced rotation in levitating wires. Levitation of the wire in a vertical configuration is achieved through magnetic forces generated by the exciting coil that balances gravitation.