Pressure sensor based on magnetic tunnel junctions

Abstract

Magnetic tunnel junctions consisting of a magnetically stable reference layer plus a magnetostrictive sense layer separated by an insulating MgO tunnel barrier have been fabricated and characterized particularly with regard to their application as strain and pressure sensors. Using a four-point-bending apparatus it has been proven that the application of mechanical stress causes the magnetization of the sense layer to rotate, while simultaneously the resistance of the strained magnetic tunnel junction changes. So far gauge factors up to 840 have been reached in resistance versus strain measurements. It has been demonstrated that these magnetic tunnel junctions also work as highly sensitive pressure gauges when placed on bulk or surface micromachined membranes.