Berlin 2008 – scientific programme

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MA: Fachverband Magnetismus

MA 22: Magnetic Particles / Clusters II

MA 22.7: Talk

Wednesday, February 27, 2008, 15:30–15:45, H 1028

Analysis of the ultra-fast in-flight heating of FePt nanoparticles. — •Elias Mohn, Darius Pohl, Ute Queitsch, Franziska Schäffel, Ludwig Schultz, and Bernd Rellinghaus — IFW Dresden, P.O. Box 270116, D-01171 Dresden,

FePt nanoparticles within a size range of 4-6 nm are prepared by DC magnetron sputtering in an inert gas atmosphere and subsequently ejected into high vacuum via differential pumping. The particles are subjected to a heat treatment in high vacuum (HV) prior to there deposition onto substrates. In contrast to earlier experiments at somewhat elevated pressures [1], the in-flight annealing of the particles is done optically, since conventional convective heating is not possible under HV conditions.

In order to determine the experimentally hardly accessible temperature of the particles, the thermal history of the particles is rather calculated from the interaction with the electromagnetic field along the flight path through the light furnace used for the in-flight annealing. The results obtained for the particle temperature are corroborated by experimental findings on the sintering of agglomerated particles.

The experiments reveal that the effect of the thermal treatment on both the structural and magnetic properties of the FePt nanoparticles strongly depends on the particles’ crystal structure before the annealing.

[1] S. Stappert et al., J. Crystal Growth 252 (2003) 440.