Fluxgate based detection of magnetic nanoparticle dynamics in a rotating magnetic field

We have developed a measurement setup allowing the investigation of the dynamics of magnetic nanoparticle suspensions in a rotating magnetic field. To determine the vector of the sample magnetization, sensitive fluxgate magnetometers are utilized detecting the sample's stray field. The phase lag between sample magnetization and rotating magnetic field vector is determined via the cross correlation spectrum. The phase lag spectra measured for various rotating field amplitudes on aqueous magnetite nanoparticle suspensions show good agreement with theory if the multidispersity of core and hydrodynamic size is taken into account. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3639276]