Improved Efficiency of Tapered Magnetic Flux Concentrators With Double-Layer Architecture

Being able to increase the sensitivity of magnetoresistive sensors, by orders of magnitude, provides a route toward challenging detection levels, and opens the way for new applications. This paper describes a novel architecture of magnetic flux concentrators to achieve an improved guiding efficiency, combining materials with different magnetic properties, and a vertical tapering. The novelty consists in the concentration of the magnetic flux kept by the entire structure in a reduced cross-sectional area within the vicinity of the spinvalve sensor. Depending on the configuration of the double-layer magnetic flux concentrators, average sensitivity gains of ~90× and ~400× were obtained. This enhanced guiding efficiency also reduced the impact of a misalignment between the device sensing direction and the applied magnetic field, since the device performance is not compromised until a misalignment angle θ = 45°. This further stabilization may arise from the vertical tapering of the magnetic flux concentrator, being consistent with 2-D finite-element simulations.