The researches on measuring constant magnetic field, DC current and soft magnetic sample’s coercivity by using atomic magnetometers are reported in this article. The accuracy and stability of the above measurements are also discussed.

The indication values of proton magnetometers and atomic magnetometers are directly proportional to the magnetic resonance frequency or Larmor precession frequency, and inversely proportional to the gyromagnetic ratio γ of protons or atoms. For the accuracy calibration of magnetometers, if the frequency measurement accuracy is high enough by using the atomic frequency standard technology, the calibration of proton magnetometers and atomic magnetometers will be transformed into the calibration of the gyromagnetic ratio γ of the working medium. The self-developed cesium magnetometer is calibrated in the magnetic induction intensity reference device. When the value of γ/2π is set to 3.49857 Hz/nT, the standard magnetic field increases from 40.5 to 80.4 μT, the error between the indication of the cesium magnetometer and the standard magnetic field measured by the proton magnetometer increases from –7.68 to –15.26 nT, and the ratio of the absolute value of the indication error to the standard magnetic field is about 1.9 × 10^–4. After modifying the value of γ/2π from 3.49857 to 3.49791 Hz/nT in the cesium magnetometer’s software, the indication error is less than 1 nT in the range of 40.5–80.4 μT, and the ratio of the absolute value of indication error to the standard magnetic field is less than 1.0×10^–5.

For the stability calibration of constant magnetic field and DC current, it is recommended to use self-excited oscillation cesium magnetometer or pump-probe atomic magnetometer, which can accurately measure the noise of reproduced magnetic field or reproduced current and avoid noise measurement distortion. We have verified the measurement capability of cesium magnetometer and pump probe rubidium magnetometer to measure magnetic field noise jumps by switching the B2912A current source range. We also use a phase-locked loop consisting of a magnetic shielding tube, magnetic field coil, voltage controlled current source, crystal oscillator, cesium magnetometer, and phase detection circuit to suppress the noise of reproduced magnetic field. When the magnetic field reproduced by the phase-locked loop is 12261.5 nT, the ratio of peak-to-peak value to the reproduced magnetic field reaches 3.3×10^–7, and the noise of the reproduced magnetic field is 0.1 pT/Hz^1/2 at 1 Hz.

To ensure traceability and accurate transmission of current values by using quantum magnetometers, the calibrations of the gyromagnetic ratio of the working medium and the coil coefficient are important metrological tasks. It is necessary to study and develop calibration specification for calculating coils or improve the calibration specification for constant magnetic field coils.

The coercivity of a soft magnetic sample is measured by a pump-probe rubidium magnetometer. When the temperature of the soft magnetic sample increases from 100 to 300 K, the coercivity decreases from 58.59 to 41.02 A/m, and the bias of hysteresis loops fluctuates around 5 A/m. When the temperature of the soft magnetic sample is 300 K, the coercivity is measured repeatedly ten times, and the measurement reproducibility is expressed as 0.17% by relative standard deviation. Related methods have the potential to be applied in the characterization of magnetic properties of soil and rock samples, as well as in satellite magnetic cleanliness control, among other applications.

The precision of high-resolution aero magnetic measurement in Criterion of Aeromagnetic Survey is better than ±1 nT. When drawing a large-area geomagnetic reference map, multiple sets of UAV aeromagnetic measurement systems need to be used simultaneously. The consistency of output values from multiple atomic magnetometers directly determines the accuracy of subsequent geomagnetic reference map splicing and processing. We suggest that the calibration of the working medium gyromagnetic ratio should be added to the proton magnetometer or atomic magnetometer calibration specification.

This article provides ideas and references for the research, development, and updating of calibration specifications and standards related to electromagnetic measurement.