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High-sensitivity magnetic field measurements are crucial in modern geoscience exploration. This study introduces an innovative free precession Bell-Bloom atomic magnetometer (FPBBAM) that exhibits a wide range of applications in geomagnetic monitoring and seismic disaster early warning due to its outstanding measurement sensitivity and low environmental requirements. The article details this magnetometer’s design principles, performance characteristics, and practical applications. It also explores how its internal mechanisms, particularly the behavior of the alkali-metal atoms (AMAs), contribute to geoscience and remote sensing applications. Extensive testing revealed that the magnetometer’s noise tolerance in a geomagnetic background exceeds $300\mathrm {pT/}(\mathrm {Hz})^{1/2}$ . However, the noise sensitivity surpasses $70~\mathrm {pT/}(\mathrm {Hz})^{1/2}$ in a shielded indoor environment. In a magnetic measurement environment with a background noise of 350 nT, the magnetic field measurement results’ root mean square error (RMSE) is better than 77.6 nT. Moreover, the magnetometer demonstrated the ability to operate stably over an extended period under challenging working conditions. This study validates the device’s real-world geoscience applications by monitoring urban spatial magnetic fields.

The Bell–Bloom atomic magnetometer is a high-sensitivity magnetic field measuring instrument. It utilizes the free precession signal of polarized atoms to obtain the magnetic field measurement. However, the complexity of the free precession signal makes it difficult for the magnetometer to measure magnetic field information, which severely limits the application of the magnetometer. In this study, to solve this problem, a free precession frequency (FPF) measurement system is designed for the Bell–Bloom atomic magnetometer, which successfully achieves accurate, fast, and efficient frequency counting of the free precession signal. Based on the analysis results of signal characteristics, the FPF measurement system was designed and tested. The equivalent instrument sensitivity can reach $\mathrm {10~pT/}(\mathrm {Hz})^{1/2}$ in the frequency range corresponding to the magnetic field of $4060~\mu T$ , and the system can work continuously for a long time. The system operates stably with independence within the temperature range of 275 350 K and can be further enhanced through an external temperature control system. Regarding measurement stability, the median repeatability of frequency measurement results exceeds 0.6 Hz. The FPF measurement system effectively addresses the complexities associated with the free precession signal and meets the magnetic field measurement requirements of the Bell–Bloom atomic magnetometer.

Accurate measurement of magnetic susceptibility plays a pivotal role in diverse scientific disciplines, ranging from material characterization to geophysical exploration. Superconducting quantum interference devices (SQUIDs) have long been regarded as the gold standard for magnetic susceptibility measurements. However, their reliance on cryogenic temperatures and complex setups imposes significant limitations. In this study, we used a single-axis spin-exchange relaxation-free (SERF) atomic magnetometer to measure magnetic susceptibility. We propose a new measurement method that resolves the inherent contradiction between the strong magnetic field and the zero-magnetic-field environment required by the SERF state in susceptibility measurements. The article provides a detailed exposition of the instrument’s principles, design, fabrication, and testing results. The achieved measured magnetic moment sensitivity is ${2} \times {10}^{-{6}}$ emu, while the coil system can realize a maximum theoretical sensitivity of ${1} \times {10}^{-{7}}$ emu. In addition, we conducted tests on actual samples and compared the results with those obtained using SQUIDs. This work demonstrates the potential of SERF atomic magnetometers in achieving low-cost, high-sensitivity measurements of magnetic susceptibility.

This brief introduces innovative approaches to assess the stability and stabilizability of nonlinear interval systems, offering efficient methods for designing state feedback stabilization controllers. Stability analysis relies on matrix theory and Lyapunov’s method, providing less conservative results compared to conventional techniques. Stabilizability analysis presents conditions for achieving stabilizability and designing feedback stabilization controller, reducing computational complexity. The effectiveness and advantages of these methods are illustrated through examples.