Magnetoelastic behaviour of a soft ferromagnetic ribbon in a silicone sheathing

The effect of a silicone sheathing on the static and dynamic magnetoelastic properties of an amorphous ferromagnetic ribbon were experimentally investigated and some simple modelling of the detected behaviour are reported. Since silicone sheath and ferromagnetic ribbon do not form alloy, it is shown that internal friction between the two component has a determining role. In the presence of static friction, magnetisation and magnetoelastic wave amplitude are prevented by the silicone sheath; but after a threshold values of the magnetising field a dump occurs towards more easy magnetisation or higher amplitude of oscillations (in resonance condition), respectively. The magnetisation curve represents a step by crossing the threshold magnetising field value; this step is very flat so that it can be used for sensors of a little magnetic field change or as switch activated by little magnetic field input. For what concerns the application of this two component material as resonator core it can be deduced that, also when a silicone sheath is present, the amplitude of resonant magnetoelastic wave is a good detector of stress, strain or local magnetic field; so that the application of magnetoelastic resonators made by amorphous ribbon core may be expanded to the cases which require a protection covering, as for example when it is necessary to work in water or in the human body