Influence of magnetic field and torsional stress on the skin penetration depth of Finemet wires

The skin penetration depth of Fe-rich wires is obtained in this work, from the impedance measurements, as a function of applied magnetic field and torsional stress. The Fe_73.5Si_13.5B₉Nb₃Cu₁ wires have been submitted to different annealing treatments in order to get the softest magnetic behaviour in the nanocrystalline state. A decrease in electrical resistivity and improvement of the soft magnetic properties of the wire annealed at 565 °C is observed. Changes in skin penetration depth of up to 36 μm are achieved with a small torsion in the nanocrystallized wire. Results can be understood by the dependence of permeability on applied magnetic field and torsional stresses.