Towards a miniature atomic scalar magnetometer using a liquid crystal polarization rotator

•Scaling of optimal pressure for a helium magnetometer with size has been modeled.•A polarization rotator is found suitable for application in atomic magnetometers.•A miniature isotropic helium-4 magnetometer has been realized.•The sensitivity of the sensor reaches 10pT/√Hz. This paper reviews the progress made in the miniaturization of an isotropic space-qualified optically pumped magnetometer. Sensor isotropy is provided by a liquid crystal polarization rotator that sets the linear pumping beam polarization at 90° with respect to the ambient magnetic field. It allows a continuous polarization rotation from 0 to more than 300° with response times compatible with mobile or space applications. This rotator is nonmagnetic and can be easily integrated close to the gas cell. The miniature helium-4 sensor reaches a sensitivity of 10pT/√Hz in a bandwidth from DC to 100Hz.