Dresden 2003 – wissenschaftliches Programm

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MA: Magnetismus

MA 6: Magnetische Partikel / Cluster

MA 6.2: Vortrag

Montag, 24. März 2003, 15:30–15:45, HSZ/04

Structural and magnetic characterization of ferrimagnetic microspheres — •Elena-Lorena Salabas, Marina Spasova, and Michael Farle — Experimentelle Tieftemperaturphysik, Gerhard-Mercator Universität Duisburg, Lotharstrasse 1, D-47048 Duisburg, Germany

The structural and magnetic properties of magnetic colloids consisting of a diamagnetic core (640 nm polystyrene) and a multi-ferrimagnetic shell (12 nm Fe3O4 nanoparticles) are discussed. The core-shell microspheres were synthesized by step-wise electrostatic adsorption. The homogeneity of the coating was characterized by transmission electron and atomic force microscopy. The aggregation process and one dimensional pattern formation in an external applied magnetic field was also investigated. In the presence of an homogeneous in plane magnetic field (0.2 T) chains with a length of up to 2 mm were formed [1]. Magnetic properties were studied by ferromagnetic resonance (FMR) and SQUID. The hysteresis loops at 5, 42, 120 and 300 K show typical features of ferromagnetic order. At low temperature (5 K) a coercivity of 245 Oe and a remanent magnetization of 39 % of the saturation value were found. Polar and azimuthal angular dependent FMR measurements at 9.51 GHz and 300 K reveal an anisotropy field (Han = 600 Oe) and a long range magnetic order in chains induced by dipole-dipole interaction.
[1] E.L. Bizdoaca et al., J. Magn. Magn. Mater.240 (2002) 44.
Supported by the Deutsche Forschungsgemeinschaft Akz. FA 209/5-1.

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