Dresden 2006 – scientific programme

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MA: Magnetismus

MA 32: Magnetic Particles / Clusters

MA 32.13: Talk

Thursday, March 30, 2006, 18:15–18:30, HSZ 401

Characterization of magnetic nanoparticles by combining magnetization, magnetorelaxometry, ac susceptibility and microscopic measurements — •Frank Ludwig, Erik Heim, and Meinhard Schilling — TU Braunschweig, Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik, Hans-Sommer-Str. 66, D-38106 Braunschweig, GERMANY

The MAgnetic Relaxation ImmunoAssay (MARIA) uses superparamagnetic nanoparticles as markers and is based on the different relaxation times and behaviour of bound and unbound magnetic nanoparticles (MNPs). A crucial point is that MARIA relies on the availability of functionalized MNPs with a proper size and narrow size distribution. We have investigated various commercially available Fe$_{3}$O$_{4}$ MNP samples with organic shell, either diluted in water or immobilized by freeze-drying, combining static M(H) curves, magnetorelaxometry (MRX), ac susceptibility as well as TEM and AFM measurements. Whereas the microscopic data reveal rather local information on size and shape of MNPs, the magnetic measurements provide integral information on their size and size distribution as well as on magnetic properties, such as anisotropy constant, saturation magnetization and Néel and Brownian relaxation times. Especially MRX using fluxgates is shown to provide more information on MNP properties than SQUID MRX since it allows one to record the whole magnetization and relaxation process of MNPs.

Financial support by the DFG via SFB 578 is acknowledged.