高灵敏度磁力仪在军用和民用的很多领域都具有非常重要的应用。目前技术上最先进的是基于超导量子干涉仪（SQUID）的磁力仪，具有很高的灵敏度，但需要超低温环境，其设备往往极为昂贵和庞大。近年来新型磁力仪的研究吸引了国际学术界的广泛关注，除追求高灵敏度之外，还需要在常温下工作，且设备小型化和便携化。本项目提出通过将超磁致伸缩材料terfenol-D与高品质因子回音壁模式光学微腔结合，实现常温工作、高灵敏、高带宽、低功耗且易于芯片集成的微型磁力仪。器件原理上，磁致伸缩材料在磁场作用下发生形变，引起微腔尺寸变化，从而造成微腔光学共振模式移动，通过传输谱非常灵敏的读出；器件制备上，我们提出采用磁控溅射法制备磁致伸缩材料于微腔中，是一种工艺简单、重复性好、可批量生产的制备方法，易于将微腔磁力仪推向实际应用。基于申请人在微腔传感、腔光力磁力仪等方面的研究基础，本项目有望实现pT/Hz1/2量级的高灵敏度。

Ultrasensitive magnetometers hold great potential in both military and civil applications. The most advanced magnetometer so far is superconducting quantum interference device (SQUID) based magnetometer, which has been applied to several fields. However, it requires cryogenic environment, making the SQUID based equipment (e.g., the commercial MEG machine in hospitals) extremely bulk and expensive. Developing room-temperature magnetometers then becomes very essential for potable and cost-effective magnetometers. In this project, we propose a cavity optomechanical magnetometry, by embedding the magnetostrictive material terfenol-D (Fe2Tb0.3Dy0.7) into a high quality whispering gallery mode microcavity. Such a hybrid system provides a kind of unique room-temperature on-chip micro magnetometer, enabling high sensitivity, broad bandwidth, and low power consumption. Specifically, the magnetic field deforms the magnetostrictive material in the cavity, thus changing the size of the cavity and then shifting the optical resonance, which can be very sensitively readout due to the very high Q of the microcavity. We propose to sputter coat terfenol-D into the microcavity, which provides a simple, highly reproducible and scalable fabrication method. The sensitivity of the microcavity optomechanical magnetometry is predicted to be of the order of pT/Hz^1/2, based on the research experience of the applicant on microcavity sensing and magnetometry.