Highly sensitive uncooled magnetometers: State of the art. Superconducting magnetic hybrid magnetometers, an alternative to SQUIDs?

We discuss the performances of highly sensitive magnetometers using flux gates, as well as magnetotransport effects (magnetoresistance - AMR/GMR and magnetoimpedance - GMI). Soft magnetic materials operating at room temperature or cryogenic temperatures are involved in these effects. We report on their performances (sensitivity, bandwidth, etc.) with emphasis on their noise properties. The latter often fall to 1-10 pT/√Hz even for active areas as low as 1-2 mm². Amorphous magnetic flux guides are often used to enhance the field sensitivity of micro-devices. Their replacement by superconducting concentrators, which could lead to much larger gain factors, is discussed. This review, together with new results, confirms a new research field which could lead to highly sensitive, low noise, superconducting-magnetic hybrid magnetometers