Diamond magnetometer enhanced by ferrite flux concentrators

TL;DR

This paper demonstrates that ferrite flux concentrators significantly enhance the sensitivity of diamond NV center magnetometers, achieving sub-picotesla sensitivity at low frequencies, which broadens their practical applications.

Contribution

The study introduces the use of ferrite flux concentrators with diamond NV sensors to improve magnetic field sensitivity, a novel approach in quantum sensing technology.

Findings

Achieved ~0.9 pT/Hz^{1/2} sensitivity between 10 and 1000 Hz.

Realized a ~250-fold increase in magnetic field amplitude within the diamond.

Utilized dual-resonance modulation to suppress thermal shifts.

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 s^{1/2}, 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 s^{1/2} to magnetic fields in the frequency range between 10 and 1000 Hz, using a dual-resonance modulation technique to suppress the effect of thermal shifts of the NV spin levels. This is accomplished using 200 mW of laser power and 20 mW of microwave power. This work introduces a new dimension for diamond quantum sensors by using micro-structured magnetic materials to manipulate magnetic fields.