Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 27: Magnetization / Demagnetization Dynamics I

MA 27.6: Vortrag

Mittwoch, 18. März 2015, 10:45–11:00, EB 301

Ultrafast demagnetization in rare-earth alloys: the role of spin-orbit coupling — •Loic Le Guyader¹, Sergej Solopow¹, Radu Abrudan^1,2, Florin Radu¹, Karsten Holldack¹, Rolf Mitzner¹, Torsten Kachel¹, Niko Pontius¹, Alexander Föhlisch¹, and Ilie Radu¹ — ¹Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany — ²Institut für Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Understanding the ultrafast demagnetization occurring upon femtosecond laser excitation of a magnetic material is a fundamental problem of modern magnetism and its microscopic origin remains highly elusive and intensely debated. Particularly, the spin-orbit coupling mediating the spin-lattice interaction is one of the key ingredients. An intriguing case of tunable parallel to anti-parallel LS coupling can be realized in rare-earth (RE) alloys. For instance, Gd60Sm40 and Gd60Dy40 alloys have similar absolute S and L, but exhibit opposite LS coupling while displaying the same ferromagnetic ordering temperature of 250 K. They constitute thus an ideal case to investigate the particular role of the LS coupling on the ultrafast demagnetization. Here we report on the properties of such RE thin film alloys using X-ray Magnetic Circular Dichroism (XMCD) with the spin and orbit sum rules at M5,4 edges. Femtosecond time-resolved transmission XMCD measurements performed at the slicing beamline reveal the element-specific demagnetization time constant in these alloys. Funding from European Union through FEMTOSPIN is gratefully acknowledged.