Regensburg 2004 – wissenschaftliches Programm

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MA: Magnetismus

MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)

MA 13.79: Poster

Dienstag, 9. März 2004, 15:00–19:00, Bereich A

Magnetization experiments on frozen ferrofluids — •O. Michele¹, J. Hesse¹, H. Bremers¹, E. K. Polychroniadis², K. G. Efthimiadis², and H. Ahlers³ — ¹Institut für Metallphysik und Nukleare Festkörperphysik, TU Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig, Germany — ²Department of Physics, Aristotle University of Thessaloniki, GR 54006 Thessaloniki, Greece — ³Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

Particle ensembles consisting of nano-Co particles fixed in space by freezing ferrofluids are investigated. In frozen ferrofluids a well defined low temperature magnetic state of the nanoparticle system can be achieved. We distinguish between textured samples (preferred orientation of easy axes) and non-textured with randomly oriented easy axes. Considering the magnetization curves of such systems bears in principle the possibility to distinguish between influences arising from particles anisotropy and particle-particle interaction. Our intention is to present new experimental strategies aiming to separate these influences from magnetization measurements versus temperature. In another approach we analyzed the susceptibility derived from magnetization measurements and determined the mean magnetic moment of the particles and an additional field which may be caused by the anisotropy of the particles or the interaction between them. Transmission electron microscopy was used for the direct measurement of the particles sizes and their size distribution.