Magnetostrictive optomechanical cavities provide a new optically-readout approach to room temperature magnetometry. Here we report ultrasensitive and ultrahigh bandwidth cavity optomechanical magnetometers constructed by embedding a grain of the magnetostrictive material Terfenol-D within a high quality (Q) optical microcavity on a silicon chip. By engineering their physical structure, we achieve a peak sensitivity of 26 pT/ √ Hz comparable to the best cryogenic microscale magnetometers, along with a 3 dB bandwidth as high as 11.3 MHz. Two classes of magnetic response are observed, which we postulate arise from the crystallinity of the Terfenol-D. This allows single-and poly-crystalline grains to be distinguished at the level of a single particle. Our results may enable applications such as lab-on-chip nuclear magnetic spectroscopy and magnetic navigation.

Aerospace technologies are crucial for modern civilization; space-based infrastructure underpins weather forecasting, communications, terrestrial navigation and logistics, planetary observations, solar monitoring, and other indispensable capabilities. Extraplanetary exploration—including orbital surveys and (more recently) roving, flying, or submersible unmanned vehicles—is also a key scientific and technological frontier, believed by many to be paramount to the long-term survival and prosperity of humanity. All of these aerospace applications require reliable control of the craft and the ability to record high-precision measurements of physical quantities. Magnetometers deliver on both of these aspects and have been vital to the success of numerous missions. In this review paper, we provide an introduction to the relevant instruments and their applications. We consider past and present magnetometers, their proven aerospace applications, and emerging uses. We then look to the future, reviewing recent progress in magnetometer technology. We particularly focus on magnetometers that use optical readout, including atomic magnetometers, magnetometers based on quantum defects in diamond, and optomechanical magnetometers. These optical magnetometers offer a combination of field sensitivity, size, weight, and power consumption that allows them to reach performance regimes that are inaccessible with existing techniques. This promises to enable new applications in areas ranging from unmanned vehicles to navigation and exploration.

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We demonstrate that an optomechanical magnetometer’s sensitivity can be improved using a high-permeability flux concentrator. The improvement depends on the geometry of the concentrator and appears to be limited by saturation of the material.