Static weak magnetic field measurements based on low-field nuclear magnetic resonance

To measure the residual magnetic field, which is a kind of static magnetic fields in the magnetic shields, is a tough task in the design of the cylindrical magnetic shields. Here, we demonstrate a method to measure static weak magnetic fields based on low-field nuclear magnetic resonance (NMR), where the static magnetic field's strength can be obtained by measuring nuclear spin precession's frequency. Atomic magnetometers can be adopted to sense the nuclear spin precession, and the nuclear spin can be adopted to measure the static magnetic field through this indirect method to obtain the static magnetic field's strength. With this method, some adverse factors that can make atomic magnetometers yield fluctuations, such as fluctuations in the light intensity and misalignment of the pump and probe beams, can be avoid. We also measure the axial residual magnetic field in the magnetic shields, where the magnetic field's strength is about 235 pT in the direction along the pump beam. By monitoring NMR signals from protons and fluorine nuclei, we realize a nuclear-spin comagnetometer, which can be used to detect static weak magnetic fields. The possibility of using a miniaturized atomic magnetometer sensor (MAMS) for static field measurements is also discussed.