Low frequency magnetic field suppression in an atomic spin co-magnetometer with a large electron magnetic field

In a K-Rb-²¹Ne co-magnetometer, the Rb electron magnetic field which is experienced by the nuclear spin is about 100 times larger than that of the K in a K-³He co-magnetometer. The large electron magnetic field which is neglected in the K-³He co-magnetometer coupled Bloch equations model is considered here in the K-Rb-²¹Ne co-magnetometer to study the low frequency magnetic field suppression effect. Theoretical analysis and experimental results shows that in the K-Rb-²¹Ne spin co-magnetometer, not only the nuclear spin but also the large electron spin magnetic field compensate the external magnetic field noise. By comparison, only the ³He nuclear spins mainly compensate the external magnetic field noise in a K-³He co-magnetometer. With this study, in addition to just increasing the magnetic field of the nuclear spins, we can suppress the magnetic field noise by increasing the density of the electron spin. We also studied how the magnetic field suppression effect relates to the scale factor of the K-Rb-²¹Ne co-magnetometer and we compared the scale factor with that of the K-³He co-magnetometer. Lastly, we show the sensitivity of our co-magnetometer. The magnetic field noise, the air density fluctuation noise and pumping power optimization are studied to improve the sensitivity of the co-magnetometer.