Antiparallel-Pinned Spin Valves With Modified Artificial Antiferromagnetic Layer for Full-Bridge Magnetic Sensors

Spin valve-based magnetic sensors are widely used in many applications for industry, science, and the life. The typical configuration of a spin valve (SV) sensor is built in a Wheatstone bridge. However, from an application point of view, the performance of the bridge depends on how high the magnetoresistance (MR) is, how effectively the opposite sensitivities of four SVs are responded, and how easily the sensor is developed. In this paper, therefore, a full bridge with four SV active cells for linear measuring applications has been engineered. The opposite sign of the MR was tuned by modifying an artificial antiferromagnetic layer that was incorporated in a typical SV structure. Two opposite meanders in the two push-pull circuits of the bridge were grown by two types of SV structures consisting of a normal MR and an inverse MR. Notably, to set the opposite sensing directions, we can use either a single post-processing field-cool anneal or the depositions of SV in a unidirectional-annealed magnetic field. A full-bridge-pinned SV sensor was patterned using the conventional lithographic liftoff method. The sensitivity of 0.23 mV/V/Oe was observed. The transfer curve (V-B) is non-hysteresis within a large linear range of ±27 Oe. The obtained features of the full bridge were consistent with the hyperbolic tangent model for designing of SV bridge sensors, and the proposed design is promising for low-field sensing, biomedical applications, and portable/wearable electronics.