Diamond current sensor integrated with a magnetic flux concentrator

Abstract

Low-frequency weak-current measurements are essential for applications such as nanoscale electronic characterization, biological ionic-current sensing, and battery leakage monitoring. While magnetometry with nitrogen-vacancy (NV) centers in diamond has been widely applied to high-current sensing, its use for ultra-weak-current detection remains relatively unexplored. Here, we demonstrate a room-temperature current sensor by integrating an NV-diamond magnetometry with a ring-shaped magnetic flux concentrator. Owing to the high permeability of the magnetic material and geometry-induced flux concentration, magnetic fields generated by ultra-weak currents are efficiently collected and enhanced at the sensor location. We achieve a current sensitivity of 0.39 nA/Hz, normalized to a single coil turn, and observe a linear transfer response with measurement deviations remaining below 3% across the tested current amplitudes and frequencies. These results provide a viable approach for extending NV-based sensing to low-frequency, ultra-weak-current regimes and offer a scalable platform for weak-signal detection in practical applications.