Hyeonjae Kim

A spin exchange relaxation-free (SERF) magnetometer is one of the most sensitive atomic magnetometers, capable of achieving fT-level sensitivity. We demonstrate a rubidium (Rb) magnetometer, operated in the SERF regime. To enter this regime, high alkali atom density and near-zero magnetic fields are required. These conditions were achieved by optimizing coil currents to null the residual magnetic field and scanning by the cell temperature. The SERF regime was experimentally verified through three observations. A sharp increase in spin relaxation time (T2) was observed in free induction decay (FID) signals as the temperature increased. The dispersion curve obtained from lock-in detection exhibited linewidth narrowing with increasing temperature and matched well with simulated results based on the Bloch equation. This setup will be used to characterize the magnetic noise of components employed in compact optically pumped atomic magnetometer (OPAM) development.