M(H) dependence and size distribution of SPIONs measured by atomic   magnetometry
  We demonstrate that the quasistatic recording of the magnetic excitation function M(H) of superparamagnetic iron oxide magnetic nanoparticle (SPION) suspensions by an atomic magnetometer allows a precise determination of the sample's iron mass content mFe and the particle size distribution. 
Simone Colombo, Victor Lebedev, Zoran D. Grujic, Vladimir Dolgovskiy   and Antoine Weis
physics.atom-ph