A magnetometer suitable for measurement of the Earth's field based on transient atomic response

We describe the development of a simple atomic magnetometer using Rb-87 vapour suitable for monitoring Earth's magnetic field. The magnetometer is based on time-domain determination of the transient precession frequency of the atomic alignment around the measured field. A sensitivity of 1.5 nT Hz(-1/2) is demonstrated by the measurement of the Earth's magnetic field in the laboratory, while for a simulated Earth field inside a magnetic shield a 130 pT Hz(-1/2) sensitivity was attained. We discuss the various parameters determining the magnetometer precision and accuracy and predict a sensitivity of 30 pT Hz(-1/2).