Characterization of Magnetic Nanoparticles for Magnetic Particle Imaging by Magnetorelaxometry, AC Susceptibility, Magnetic Particle Spectroscopy and Static Magnetization Measurements

To investigate various magnetic nanoparticle samples for their suitability as markers for Magnetic Particle Imaging (MPI), various magnetic techniques can be applied. Whereas Magnetic Particle Spectroscopy (MPS) directly provides the harmonic spectrum for a given excitation frequency and ac field amplitude, for the design of optimal markers, it is important to relate the measured harmonic spectra to specific nanoparticle properties. We have applied fluxgate magnetorelaxometry (MRX), ac susceptibility (ACS) up to 1 MHz, multivariate MPS - varying the excitation field amplitude and frequency as well as the magnitude of a superimposed dc field - and static magnetization measurements for the comprehensive characterization of representative magnetic nanoparticle samples. To distinguish between core and hydrodynamic properties, aqueous suspensions as well as immobilized samples were investigated.