A micromachined magnetostrictive pressure sensor using magneto-optical interrogation

In this paper we present the first micromachined, magnetostrictive membrane -type pressure sensor. The proof-of-principle device is based on a micromem brane coated with a magnetostrictive thin-film and magneto-optical interrog ation. A pressure difference across the diaphragm causes deflection and thu s stress in the magnetostrictive layer. This leads to a change in the magne tic properties of the thin-film, which can be detected using the Magneto-Op tical Kerr Effect (MOKE). For good sensor response the choice of membrane s hape is considered. High aspect-ratio, rectangular membranes are found to p roduce uniaxial stress over a large area, leading to a well-defined uniaxia l magnetic anisotropy in the piezomagnetic thin-film. Silicon nitride membr anes sputter-coated with a soft-magnetic, magnetostrictive layer similar in composition to METGLAS(R) 2605-SC have been fabricated. The samples are an alysed magnetically by MOKE and the membrane deflection is determined with an interferometer. Both the magnetic and mechanical data is compared to the oretical predictions. (C) 2000 Elsevier Science S.A. All rights reserved.