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MA: Magnetismus

MA 32: Magnetic Particles / Clusters

MA 32.8: Vortrag

Donnerstag, 30. März 2006, 17:00–17:15, HSZ 401

Enhanced orbital magnetism in oxide-free FePt nanoparticles — •C. Antoniak¹, K. Fauth^2,3, H.-G. Boyen⁴, U. Wiedwald⁴, F. Wilhelm⁵, A. Rogalev⁵, M. Spasova¹, J. Lindner¹, M. Acet¹, and M. Farle¹ — ¹Fachbereich Pysik, Universität Duisburg-Essen, Lotharstr. 1, D-47048 Duisburg — ²MPI für Metallforschung, Heisenbergstr. 3, D-70689 Stuttgart — ³Experimentelle Physik IV, Universität Würzburg, Am Hubland, D-97074 Würzburg — ⁴Abteilung Festkörperphysik, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm — ⁵European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, B.P. 220, F-38043 Grenoble

Wet chemically synthesised Fe₅₀Pt₅₀ particles with a mean diameter of 6.3 nm deposited on a naturally oxidised Si substrate have been structurally and magnetically characterised. By a soft hydrogen plasma treatment, the oxide shell and the organic ligands surrounding the chemically disordered particles in the as prepared state were removed and pure metallic x-ray absorption and magnetic circular dichroism spectra were measured at both the Fe and Pt L_3,2 edges. After annealing for 30min at 600^∘C in a hydrogen atmosphere of 5 Pa, the coercive field increased by a factor of 6. This indicates the formation of the chemically ordered L1₀ phase and is accompanied by an enhancement of the orbital magnetic moment at the Fe sites by more than 300%, whereas the magnetic moments at the Pt sites remain largely unchanged.
This work was supported by the BMBF (05 ES3XBA/5), the ESRF, the DFG (SFB 445) and the EU (MRTN-CT-2004-0055667, SyntOrbMag).