Dresden 2003 – wissenschaftliches Programm
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MA: Magnetismus
MA 19: Mikro- und nanostrukturierte Materialien I
MA 19.2: Vortrag
Mittwoch, 26. März 2003, 15:30–15:45, HSZ/405
Small-Angle X-ray Scattering Analysis and Magnetic Characterization of Self-assembled Nanoparticles. — •Keir Foster1, Jörg Weissmüller1,2, Raghavan Nadar Viswanath1, Dominik Kramer1, Branko Stahl3, and Jens Ellrich3 — 1Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe, Germany — 2Universität des Saarlandes, Fachrichtung Technische Physik, Saarbrücken, Germany — 3U Darmstadt, Materials Science Dep., Petersenstr. 23, 64287 Darmstadt, Germany
A small-angle X-ray (SAXS) study and magnetic characterization of dilute and non-dilute samples of FePt nanoparticles suspended in hexane have been conducted. Particle-size distributions were derived from the SAXS data for dilute samples via a maximum entropy method. A mean particle size of 4.0 nm was obtained, in good agreement to that determined by transmission electron microscopy. SAXS measurements on more condensed samples show a series of clear maxima for q =1−4 nm−1 indicating a degree of local ordering is present. Magnetic characterization by vibrating sample magnetometry (VSM) and AC susceptibility measurements indicate superparamagnetic behaviour with a blocking temperature of TB = 13,1 +/- 0,3 K. The real component of the susceptibility showed frequency dependent maxima for measurement frequencies of 0,1-10 kHz and were successfully analysed in terms of the Neel theory of superparamagnetism. The crucial role of sample concentration on the inter-particle distance, and hence on the dipole-dipole interactions between particles, and how this effects the observed magnetic properties will be discussed.