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

## TL;DR

This paper introduces a new method to improve the sensitivity and performance of diamond-based magnetometers for better practical use.

## Contribution

A dual-magnetic-resonance-frequency-locking differential detection method is proposed to enhance sensitivity and enable AC magnetic field detection.

## Key findings

- The scaling factor between sensor output and magnetic field is doubled compared to the single-MRFL method.
- The proposed method achieves a sensitivity of 0.56 nT/√Hz, a 58.2% improvement over the single-MRFL method.
- The system can detect AC magnetic fields with a measurement range from −0.29 mT to 0.30 mT.

## Abstract

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.