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MA: Fachverband Magnetismus

MA 16: Magnetization and Demagnetization Dynamics I

MA 16.10: Talk

Tuesday, March 8, 2016, 12:00–12:15, H34

Standing spin waves excited by spatially non-uniform ultrafast spin transfer torque in Fe/Au/Fe/MgO(001) multilayer — Ilya Razdolski¹, Alexandr Alekhin¹, Nikita Ilin¹, Jan Meyburg², Detlef Diesing², Vladimir Roddatis³, Uwe Bovensiepen⁴, and •Alexey Melnikov¹ — ¹Fritz-Haber-Institut der MPG, Abt. Phys. Chemie — ²Universität Duisburg-Essen, Institut für Phys. Chemie — ³Universität Göttingen, Institut für Materialphysik — ⁴Universität Duisburg-Essen, Fakultät für Physik

Ultrafast spin dynamics is the key for development of data storage and spintronics devices. Of particular interest is the generation of ultrashort spin current (SC) pulses and the study of their subsequent spin transfer torque (STT) action on a ferromagnet. We excite non-equilibrium spin-polarized hot carriers (HC) in a top Fe layer of a Fe/Au/Fe/MgO(001) structure by 14 fs-long 800 nm laser pulse. Traversing the Au layer, these HC form SC pulses which are detected by the second harmonic generation: we demonstrate about 300 fs-long SC pulses in Au. When the HC reach the second, 15 nm-thick Fe layer, its magnetization (if it is non-collinear to the HC spin) experiences a torque and starts moving out of the equilibrium. Thus excited picosecond precessional dynamics of the magnetization is monitored by the magneto-optical Kerr effect. We show that owing to a spatially non-uniform STT, on top of the uniform precession, several lowest standing spin wave modes can be excited. Spectral analysis of the excited modes allows for an estimation of the STT depth in Fe to below 2 nm. DFG (ME 3570/1, Sfb 616) and EU 7-th framework program (CRONOS) are acknowledged.