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MM: Fachverband Metall- und Materialphysik
MM 38: Nanostructured Materials V
MM 38.2: Vortrag
Donnerstag, 28. Februar 2008, 12:00–12:15, H 0111
The influence of ion irradiation on bimetallic nanoparticles — •Darius Pohl1, Elias Mohn1, Jürgen Fassbender2, Karsten Albe3, Ludwig Schultz1, and Bernd Rellinghaus1 — 1IFW Dresden, D-01171 Dresden, Germany — 2Forschungszentrum Rossendorf, D-01314 Dresden, Germany — 3TU Darmstadt, D-64287, Germany
FePt nanoparticles with mean diameters of about 5 nm and a narrow particle size distribution are prepared through inert gas condensation. Since as-deposited particles usually exhibit the metastable disordered and soft magnetic A1 phase or even other structural motifs such as icosahedral or decahedral multiply twinned structures, additional annealing steps are required to transform these particles into the L10 phase.
In order to gain more insight into the phase stability of the various crystal structures observed in FePt nanoparticles we have investigated, how ion irradiation influences these structures. Comparable studies were conducted on particles of CuAu, the phase diagram of which is very alike that of FePt. In the present study, gas-phase prepared single crystalline and multiply twinned FePt and CuAu nanoparticles are irradiated with ions of different noble gases and different energy. It is shown that the He+ ion irradiation promotes the de-twinning of the bimetallic nanoparticles and the formation of single crystalline A1 phase particles. A comparison of the experiments on CuAu nanoparticles with the results of molecular dynamic simulations will be presented. The effect of the energy difference between the different morphologies for both the ordered and disordered structures is discussed.