Magnetoelectronical Sensors for Mechanical Measurements

Abstract

Recently, highly sensitive strain gauges were developed, which are based on TMR (tunnel magnetoresistance) or GMR (giant magnetoresistance) effects combined with the inverse magnetostriction. GMR and TMR structures generally possess a symmetrical characteristic which reflects the switching fields of the soft and hard layers, respectively. This characteristic can be changed by a stress field if the soft layer is replaced by a suitable magnetostrictive layer leading to a stress induced rotation of the magnetostrictive layer with respect to the reference layer. In particular in combination with the TMR effect, this approach illustrates an interesting, highly sensitive mechanism in order to detect mechanical variables with a high spatial resolution as well as an unrivaled high gauge factor. In addition, the feasibility of an integrated fabrication compatible to cost effective fabrication routes using nano-/micro techniques is of great interest e.g. for the automotive industry. In this paper, the basics, the fabrication and the features of magnetoelectronical sensors will be discussed in view of an integrated pressure sensor for automotive applications.