Enhanced Output Performance in Spin-Valve Bridge Sensors by a Compound Nanostructure for Ferromagnetic Free Layers

The linear response is one of the most critical technical parameters of a spin-valve bridge sensor. Since the material properties of ferromagnetic free layers play an important role in the operation mechanism of the linear response to an external magnetic field, we propose a compound nanostructure of ferromagnetic free layers. The nanostructure is composed of spin polarization ( P )/magnetostrictive bilayers. To systematically investigate the variation in P value and uniaxial magnetic anisotropy constant ( K ) introduced by magnetostrictive materials, we performed a micro-magnetic simulation to assess the output properties of the bridged spin-valve sensor. The change in magnetization ( M ), resistance ( R ) and the ratio of the output voltage ( U o ) to the input voltage ( U i ) for the bridge with magnetic field strength ( H ) was quantitatively calculated. It was found that when the magnitude of K varied between 2 × 10 4 J/m 3 and 10 5 J/m 3 , the output linear range was significantly manipulated, increasing from ± 350 Oe to ± 690 Oe, though the sensitivity showed a small decrease from 1.6 × 10 −4 to 4.0 × 10 −‍5 . However, when P varied from 0.2 to 1.0, the sensitivity increased linearly. The results confirmed that the compound nanostructures with larger P and additive K are effective for realizing continuous regulation and a larger linear output range for spin-valve bridge sensors.