Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Invited Talks Suga / Münzenberg

MA 6.2: Hauptvortrag

Montag, 25. Februar 2008, 14:30–15:00, EB 301

Probing spin excitations in magnetic nanostructures and half metals — •Markus Münzenberg — IV. Phys. Institute, University of Göttingen

The understanding of single spin-flip processes, ps pulsed excitation of magnetic spin packets and spin currents is of importance to develop a magnetic switching concept for spin-electronic devices beyond the 50 ps time scale. A tool to study these processes is the demagnetization by intense laser pulses. The first systems presented are half metals. They are most interesting because of their electronic properties; in particular the peculiar property that one spin-channel has no states at the Fermi energy: the ultrafast electronic demagnetization channel via spin-flip processes is prohibited. Only the very slow channel, via anisotropic fluctuations of the crystal field, thermalizes the spin system with the lattice. This can be used as a new method to identify the half metallic character of a material. Second, in magnetic nanostructures magnetic inhomogeneities are generated and self amplified in spin-torque experiments. Here I will present mechanisms that connect the high energy spin waves with the magnetic eigen modes of the nanostructures. The mechanism generates a broad spectrum of modes that can be identified by a resistance reduction or increase respectively. The experiments support the role of an Elliot-Yafet type like electron-spin interaction responsible for the THz response of the ultrafast demagnetization in ferromagnets. Research was supported by the DFG priority research program 1133 Ultrafast magnetization processes.