Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 2: Magnetic Particles/Clusters I
MA 2.8: Vortrag
Montag, 26. März 2007, 12:00–12:15, H10
Magnetic Anisotropy of fcc and L10 ordered FePt nanoparticles — •Ulf Wiedwald1, Andreas Klimmer1, Luyang Han1, Birgit Kern1, Kai Fauth2, Hans-Gerd Boyen1, and Paul Ziemann1 — 1Institut für Festkörperphysik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm — 2Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, 70569 Stuttgart
FePt alloy nanoparticles exhibit huge magnetic anisotropy energy in the chemically ordered L10 phase. This ordered phase is typically obtained by annealing the as-prepared chemically disordered fcc FePt nanoparticles at 600-800∘C. Such fcc FePt nanoparticles can also be fabricated by a micellar technique resulting in regular arrays on various substrates. This approach offers the advantage that the interparticle distance can be tuned between 20-100 nm allowing to completely suppress particle agglomeration during the annealing induced transformation into the L10 phase. Moreover, the particles are magnetically decoupled. We investigated the formation of the L10 phase for 3-10 nm FePt particles as a function of the annealing temperature and time. For this purpose, the structural transformation is tracked by magnetic hysteresis loops taken at various temperatures after each annealing step. In case of 9 nm particles we observe a coercive field of µ0 H = 0.2 T at 340 K. For particles smaller than 6 nm preliminary results indicate an at least impeded structural transformation.