High-Sensitivity Operation of Unshielded Radio Frequency Atomic Magnetometers Using Phase-Lock Techniques

High sensitivity operation of radio-frequency atomic magnetometers in unshielded environment requires compensation of low-frequency fluctuations of the ambient magnetic field. Here we demonstrate the use of phase-lock techniques to stabilise the magnetic environment and achieve high sensitivity at high frequencies. This is achieved by using the output of the atomic magnetometer both for stabilisation and for measurement purposes. The approach is validated by a proof-of-concept in unshielded environment. The phase-lock approach is also compared to the standard approach where the magnetic environment is stabilised with the help of a set of fluxgate magnetometers, and it is shown that the phase-lock approach features superior performances in signal detection.