Design and Properties of a Thin-Film, Mems-Based Magnetostrictive Magnetometer

The principles of operation of a MEMS-based magnetometer designed on the magnetoelastic effect are described. The active transduction element is a commercial (001) silicon microcantilever sputter coated with an amorphous thin film of the giant magnetostrictive alloy Terfenol-D [(Dy 0.7 Tb 0.3 )Fe 2 ]. The easy axis of magnetization of the Terfenol-D film lies in the plane of the microcantilever and along the acicular direction. In addition to the magnetostrictive transducer, basic components include: (a) mechanical resonance of the coated-microcantilever through coupling to an ac magnetic field; and, (b) detection by optical beam deflection of the microcantilever motion utilizing a laser diode source and a position-sensitive detector. The sensitivity of this magnetostrictive magnetometer is currently 1 μT, which is three orders of magnitude better than a magnetometer based on a similar-sized piezoresistive cantilever.