Dresden 2006 – wissenschaftliches Programm
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MA: Magnetismus
MA 7: Micro- and Nanostructured Magnetic Materials I
MA 7.10: Vortrag
Montag, 27. März 2006, 17:15–17:30, HSZ 03
In flight optical heating of FePt nanoparticles — •Elias Mohn, Franziska Schäffel, Christine Mickel, Bernd Rellinghaus, and Ludwig Schultz — IFW Dresden, P.O. Box 270116, D-01171 Dresden
Monodisperse fractions of FePt nanoparticles are prepared by DC magnetron sputtering in an inert gas atmosphere at elevated gas pressures. Subsequent ejection into high vacuum results in an increase of the mean free path of the particles and thereby allows to substantially suppress inter-particle coalescence and sintering. In order to benefit from the high magnetic anisotropy of L10 ordered FePt without sacrificing monodispersity, the particles are to be subjected to in-flight thermal annealing prior to their deposition to establish the chemically ordered tetragonal phase. Since convective in-flight heating [1] is no longer efficient in high vacuum, optical heating is applied. We have therefore developed a UHV compatible light furnace, in which the light of 3 halogen lamps (with a power of up to 1.2 kW each) is focussed on the particles’ flight path at a length of 150 mm. The crystal structure of the particles is characterized by means of TEM. The status quo of these experiments is reported. First investigations reveal the occurrence of recrystallization twins in the particles upon switching on the light furnace. This indicates an effective heat transfer from the electromagnetic field to the particles. The experimental results are corroborated by model calculations of the energy transfer based on classical electrodynamics. The dependence of the heating rate on the particle size is discussed.
[1] S. Stappert et al., J. Cryst. Growth 252 (2003) 440-450.