Designs and Characterizations of Soft Magnetic Flux Guides in a 3-D Magnetic Field Sensor

A 3-D magnetic field sensor based on the giant magnetoresistive (GMR) spin valve (SV) was designed for improving the energy efficiency in intelligent automating devices. Generally GMR SV sensors are selective only in the plane of the substrate due to fabrication restraints. For this application, a sensor with ultra-thin dimensions is required for the system integration. The approach using micro-assembly for the accomplishment of 3-D field detection is not possible. Therefore, the integration of soft magnetic materials is essential to deflect the magnetic flux for the detection of a magnetic field in the direction perpendicular to the substrate. In this paper the design of 3-D flux guides was presented. Finite element method (FEM) simulations were used to optimize the flux guide design. NiFe, with its high permeability μ, low coercivity H_c and relatively high saturation flux density B_s, was regarded as the suitable material for this application. Electroplating and patterning by means of photolithography promises to be the appropriate process to integrate this material after the deposition of the GMR multilayer. To characterize the magnetic properties measurements with a Vibrating Sample Magnetometer (VSM) as well as a hysteresisgraph were carried out.