Abstract
Magnetometers based on nitrogen-vacancy (NV) centers in diamond are promising room-temperature, solid-state sensors. However, their reported sensitivity to magnetic fields at low frequencies (≾1 kHz) is presently ≿10 pT s1/2, precluding potential applications in medical imaging, geoscience, and navigation. Here we show that high-permeability magnetic flux concentrators, which collect magnetic flux from a larger area and concentrate it into the diamond sensor, can be used to improve the sensitivity of diamond magnetometers. By inserting an NV-doped diamond membrane between two ferrite cones in a bowtie configuration, we realize a ~250-fold increase of the magnetic field amplitude within the diamond. We demonstrate a sensitivity of ~0.9 pT s1/2 to magnetic fields in the frequency range between 10 and 1000 Hz. This is accomplished using a dual-resonance modulation technique to suppress the effect of thermal shifts of the NV spin levels. The magnetometer uses 200 mW of laser power and 20 mW of microwave power. This work introduces a new degree of freedom for the design of diamond sensors by using structured magnetic materials to manipulate magnetic fields.
Highlights
Quantum sensors based on nitrogen-vacancy (NV) centers in diamond have emerged as a powerful platform for detecting magnetic fields across a range of length scales [1]
We demonstrate a sensitivity of ∼0.9 pT s1/2 to magnetic fields in the frequency range between 10 and 1000 Hz
We show that the combination of flux concentration and dual-resonance modulation enables diamond magnetometry with sub-pT s1/2 sensitivity over a broad frequency range
Summary
Quantum sensors based on nitrogen-vacancy (NV) centers in diamond have emerged as a powerful platform for detecting magnetic fields across a range of length scales [1]. A diamond magnetometer based on infrared absorption detection realized a sensitivity of ∼30 pT s1/2 at 10–500 Hz, using 0.5 W of laser power [18]. To understand the interplay between sensitivity and laser power, we consider a diamond magnetometer based on continuous-wave, fluorescence-based optically detected magnetic resonance (ODMR). Is needed to realize a sensitivity of 1 pT s1/2, and further improvements become impractical The need for such a high laser power presents challenges for thermal management and has implications for the overall sensor size, weight and cost. With further improvements, a magnetic noise floor of ∼0.02 pT s1/2 at 1000 Hz is possible before ferrite thermal magnetization noise limits the sensitivity
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