From magneto-elastic impedance model to accurate magneto-mechanical coefficient measurements

The measurement of the magneto-elastic impedance enables the magneto-mechanical coefficient of amorphous tapes, for example, to be accurately estimated. We first propose an analytical model describing the principle of a resonator based on magnetostrictive ribbons. We show how, from the impedance described by a circle in the complex plane, the characteristics of a magnetostrictive resonator can be established and estimated from the evolution of the impedance as a function of frequency. This method, which is entirely implemented with an amorphous metal ribbon (Metglas^™ 2826), is perfectly adapted to estimate the magneto-mechanical coupling coefficient k₃₃ and thus establish the magnetostriction curves λ(H) of amorphous ribbons. However, application to thick nickel foil shows that the current method is restricted to magnetic materials in a thin ribbon form (<∼100 µm). It should also be noted that this technique has serious advantages over those commonly used: it is non-destructive, inexpensive, and very easy to use.