Highly Sensitive SAW-Based Magnetic Field Sensors With Suppressed Domain Wall Noise

As an emerging technique, surface acoustic wave (SAW)-based magnetic field sensors offer pT-level sensitivity, broad-band detection ability and flexibility to deploy smart sensor networks. The primary noise of this type of sensor is magnetic loss introduced by the interaction between SAWs and domain walls. In current work, dual-mode SAW delay-line-type magnetic field sensors were designed and fabricated. Our measurement results reveal that proper selection of the operation frequency can significantly increase magnetic field sensitivity while reducing magnetic phase noise due to domain wall resonance (DWR). In addition, tailoring the geometry of magnetic film can also reduce domain wall density along the SAW propagation path, and thus lower magnetic phase noise. These efforts lead to an optimized device with an ultrahigh sensitivity of 1630.3 deg/mT and a low limit of detection (LOD) of 378.2 pT/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sup> at 10 Hz.