Alternative magnetic field sensor based on modified yttrium iron garnet (YIG) microspheres and a magnetostrictive material

This article demonstrates a novel approach to alternating current (AC) magnetic field detection using a yttrium iron garnet (YIG) microsphere combined with magnetostrictive materials. The sensing system utilizes an optical fiber taper to couple light in and out of the YIG microsphere and changes in the transmission spectrum to reflect the magnetic field variations. Three configurations are investigated: YIG microsphere with FeGa sheet, Terfenol-D sheet, and Terfenol-D sheet plus polydimethylsiloxane (PDMS) coating. The system successfully detects AC magnetic fields in the frequency range from 100 to 500 kHz. Initial measurements using FeGa sheets achieved a sensitivity of 107.7 nT/root Hz. Replacing FeGa with Terfenol-D improved the sensitivity approximately three-fold due to its larger magnetostriction coefficient. Further enhancement was achieved by coating the YIG microsphere with PDMS, which improved the optical quality factor by 2.4 times and yielded an optimal sensitivity of 53.51 nT/root Hz at 322.3 kHz. These results demonstrate the potential of YIG microsphere-based systems for high-sensitivity magnetic field detection, offering advantages such as simple structure, low cost, and easy integration. The ability to improve sensitivity through material selection and surface modification suggests promising applications in integrated photonics systems and magnetic field monitoring.