Sensitivity Improvement via Differential Detection for Frequency-Locking Diamond Magnetometers.

The magnetic resonance frequency-locking technique is recognized as an effective approach for simultaneously improving the dynamic range, performance stability, and measurement precision of diamond nitrogen vacancy (NV)-center magnetometers. Nevertheless, insufficient research on sensitivity limits the overall performance of frequency-locking diamond magnetometers. In this paper, we propose a dual-magnetic-resonance-frequency-locking (MRFL) differential detection method. Theoretical and experimental results demonstrate that the scaling factor between the sensor output and the magnetic field is doubled compared with that under the single-MRFL method, and the proposed method also enables alternating current (AC) magnetic field detection. The proposed system exhibits a measurement range from -0.29 mT to 0.30 mT. Furthermore, a sensitivity of 0.56 nT/√Hz is achieved, representing a 58.2% improvement relative to that of the single-MRFL method. Our work provides a viable solution for accelerating the transition of frequency-locking diamond magnetometers from laboratory research to practical applications.