Regensburg 2007 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 10: Layers with Magnetic Properties

DS 10.6: Vortrag

Montag, 26. März 2007, 18:30–18:45, H34

Magnetization in homogenous ferrofluidic films — •Birgit Graf¹, George Tzvetkov¹, Jörg Raabe², Konstantin Petukhov³, and Rainer Fink¹ — ¹Universität Erlangen-Nürnberg, Lehrstuhl für Physikalische Chemie II, Erlangen, Germany — ²Paul Scherrer Institut, Villigen, Switzerland — ³Universität Erlangen-Nürnberg, Physikalisches Institut III, Erlangen, Germany

Ferrofluids are comprised of microscopic ferromagnetic nanoparticles, usually magnetite (Fe₃O₄), hematite (Fe₂O₃) or some other compound containing Fe²⁺ or Fe³⁺ suspended in a carrier fluid. The nanoparticles are typically of order 1-10 nm. Therefore and because of the fact that they are usually coated with a surfactant, most of the ferrofluids are stable. Since they do not retain magnetization in the absence of an externally-applied field they do not display macroscopic ferromagnetism.

As a model substance, we investigated thin films of APG L23 (from FerroTec, Nürtingen), which were prepared by spin-coating of the low viscous material. This material consists mainly of 10 nm magnetite particles. Using scanning transmission x-ray microscopy (STXM) at the SLS PolLux beamline we could monitor small inhomogeneities within the films, which show distinct variations in the Fe L-Edge spectra. These variations may be due to phase separated species with different oxidation states. Using XMCD spectra and SQUID measurements, we derive the magnetic properties of differently prepared films (funded by the BMBF, contract 05 KS4 WE1/6).