Characterization of magnetostrictive TMR pressure sensors by MOKE

Abstract

Magnetostrictive tunneling magnetoresistive (TMR) pressure sensors have been developed by combining micro electrical–mechanical systems (MEMS) fabrication techniques with magnetic thin film technology. The sensing TMR elements with magnetostrictive Fe 50Co 50 free layers were placed on different positions on a 2-μm-thick Si membrane structure allowing localized strain measurements. Compressive or tensile mechanical strain up to 0.12% can be introduced by applying different air pressure (0.1–4 bar) to the sealed membrane cavity, which in turn leads to a change in the magnetization direction due to the inverse magnetostrictive effect. For the first time, the strain-induced switching of the free layers has been characterized by means of magneto-optical Kerr effect (MOKE) measurements.