Hybrid NV Center Magnetometer With Directional Vector Resolution Based on Magnetic Flux Concentrators

Since the introduction of Hall magnetometers, different types of magnetometers have been widely used. Among them, magnetometers based on nitrogen-vacancy (NV) centers in diamonds are promising room-temperature solid-state sensors. Their sensitivity to low-frequency (< 10 Hz) magnetic fields has been reported to be currently at the nanotesla level. Still, limitations in the detectable spatial range hinder their potential applications in medical imaging, earth sciences, and navigation. The most recent sensitivity enhancement technique involves using high-permeability flux concentrators with a unique magnetic field amplification structure that can cause the NV magnetometer to lose its vector detection capabilities. To address this limitation, we proposed a hybrid magnetometer based on a diamond-based hetero-NV center, which collects magnetic flux over a larger area and concentrates it in the diamond magnetometer, from which the magnetic field vector can be calculated by measuring the specific magnetic field direction vector. The low-frequency sensitivity of 90 pT $\cdot $ Hz $^{{(!{-}!){1}/{2}}}$ under conventional ambient conditions has been solved by inserting NV-doped diamond blocks between four permalloy concentrators in a triangular structure, which solves the vector deficiency problem of traditional magnetic concentrators. High-sensitivity real-time variation acquisition of the magnetic field signal has been achieved by applying an ac magnetic field in combination with modulation and demodulation methods.