Regensburg 2007 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 6: Magnetic Particles/Clusters II
MA 6.6: Vortrag
Montag, 26. März 2007, 16:30–16:45, H10
L10-ordering of FePt nanoparticles by in-flight optical heating — •Elias Mohn, Darius Pohl, Franziska Schäffel, Ludwig Schultz, and Bernd Rellinghaus — IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
FePt nanoparticles with sizes in the range of 4-6 nm are prepared by DC-magnetron sputtering in argon. Upon leaving the nucleation and growth chamber, the particles are ejected into high vacuum via differential pumping. This allows to effectively control both the degree of agglomeration and the primary particle size. Prior to their deposition, the particles are heated in flight by means of a newly constructed paraxial light furnace. Transmission electron microscopy (TEM) investigations reveal that upon increasing the furnace power, particle agglomerates successively coalesce, and fully sintered spherical particles are formed at powers of P ≥ 3 kW. This proves that effective radiative heating of the particles is accomplished even though the heating times are as short as 1 ms. A comparison of these findings with recent experiments of Stappert et al. [1] allows to estimate a minimum particle temperature of T ≥ 800 oC at P = 3 kW. Structural characterization by high resolution TEM reveals the onset of the L10 order in likewise treated FePt nanoparticles. This goes along with an increase of the coercivity which is, however, substantially smaller as compared to that of fully ordered FePt thin films. The obtained results are analyzed with respect to the L10 ordering kinetics. They confirm our assumption that the ordering is predominantly governed by volume diffusion. [1] S. Stappert et al., J. Cryst. Growth 252 (2003) 440.