Development of an integrated magnetic sensor with linear output based on spin valves

Abstract

The particular objective in this article is to develop a sensor with high sensitivity and linear output that crosses zero at zero field. The sensor is an integrated magnetic device based on a Wheatstone bridge of micropatterned spin valve resistors with the addition of a soft magnetic structure that determines the principal characteristics of the sensor. This magnetic structure is a soft layer shaped to guide the magnetic flux lines of the external magnetic field to the proximity of the bridge elements with the desired angle. With this configuration we change the local field direction rather than the local anisotropy of the spin valve material in order to set up the bridge. The sensitivity of the sensor strongly depends on the permeability of the soft adjacent layer, hence it is significantly increased even in a nonoptimized device, considering other magnetoresistance devices currently available. The sensitivity reported for this device is ∼0.2 %/μT.