Detecting rotating magnetic fields using optically pumped atomic magnetometers for measuring ultra-low-field magnetic resonance signals

In this paper, we describe the detection of rotating magnetic fields using optically pumped atomic magnetometers (OPAMs) for measuring magnetic resonance (MR) signals. From the results of rotating- and alternating-magnetic-field measurements, we found that to detect a rotating magnetic field with high sensitivity, the rotation direction of the magnetic field to be measured must select the bias-magnetic-field direction of OPAM. In addition, the OPAM sensitivity for rotating magnetic fields should be twice that for alternating magnetic fields. These results indicate that for measuring MR signals, magnetic fields caused by rotating magnetizations can be detected with the sensitivity of 10 fT(rms)/root Hz order at 1 kHz using OPAMs. (C) 2012 Elsevier Inc. All rights reserved.