Highly Sensitive Magnetic Sensor Based on Anisotropic Magnetoresistance Effect

The magnetic field sensors based on anisotropic magnetoresistance (AMR) effect have been widely used in data storage, navigation, and medical diagnosis. However, the AMR effect of metal materials is relatively weak with an AMR ratio below 2%, which results in low voltage output. In order to improve the sensitivity of weak magnetic fields, we optimize the structure of the AMR sensor with a specific photolithographic process. We use two different designs of Hall bar and Wheatstone bridge with similar barber pole structures, and investigate the angular dependence as well as magnetic field dependence of AMR ratio and voltage output. With Wheatstone bridge, the magnetoresistance leads to a voltage output without dc components. The NiFe magnetic layer and the Au electrode are patterned into a highly conductive barber poles structure, and a high voltage output ratio of about 80% is obtained. At the same time, we achieve a high sensitivity of about 4.3 Oe^-1, which implies potential applications in AMR effect-based magnetic field sensors.