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Proceedings Paper

Ultrafast spintronics roadmap: from femtosecond spin current pulses to terahertz non-uniform spin dynamics via nano-confined spin transfer torques (Conference Presentation)
Author(s): Alexey Melnikov; Ilya Razdolski; Alexandr Alekhin; Nikita Ilin; Jan Meyburg; Detlef Diesing; Vladimir Roddatis; Ivan Rungger; Maria Stamenova; Stefano Sanvito; Uwe Bovensiepen
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Paper Abstract

Further development of spintronics requires miniaturization and reduction of characteristic timescales of spin dynamics combining the nanometer spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the spin transfer torque (STT) exerted by ultrashort SC pulses on the FM open the time domain for studying STT fingerprint on spatially non-uniform magnetization dynamics. Using the sensitivity of magneto-induced second harmonic generation to SC, we develop technique for SC monitoring. With 20 fs resolution, we demonstrate the generation of 250 fs-long SC pulses in Fe/Au/Fe/MgO(001) structures. Their temporal profile indicates (i) nearly-ballistic hot electron transport in Au and (ii) that the pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Together with strongly spin-dependent Fe/Au interface transmission calculated for these carriers, this suggests the non-thermal spin-dependent Seebeck effect dominating the generation of ultrashort SC pulses. The analysis of SC transmission/reflection at the Au/Fe interface shows that hot electron spins orthogonal to the Fe magnetization rotate gaining huge parallel (anti-parallel) projection in transmitted (reflected) SC. This is accompanied by a STT-induced perturbation of the magnetization localized at the interface, which excites the inhomogeneous high-frequency spin dynamics in the FM. Time-resolved magneto-optical studies reveal the excitation of several standing spin wave modes in the Fe film with their spectrum extending up to 0.6 THz and indicating the STT spatial confinement to 2 nm.

Paper Details

Date Published: 4 November 2016
PDF: 1 pages
Proc. SPIE 9931, Spintronics IX, 99311A (4 November 2016); doi: 10.1117/12.2239214
Show Author Affiliations
Alexey Melnikov, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany)
Ilya Razdolski, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany)
Alexandr Alekhin, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany)
Nikita Ilin, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany)
Jan Meyburg, Univ. Duisburg-Essen (Germany)
Detlef Diesing, Univ. Duisburg-Essen (Germany)
Vladimir Roddatis, Institut für Materialphysik, Universität Göttingen (Germany)
Ivan Rungger, Trinity College Dublin (Ireland)
Maria Stamenova, Trinity College Dublin (Ireland)
Stefano Sanvito, Trinity College Dublin (Ireland)
Uwe Bovensiepen, Univ. Duisburg-Essen (Germany)

Published in SPIE Proceedings Vol. 9931:
Spintronics IX
Henri-Jean Drouhin; Jean-Eric Wegrowe; Manijeh Razeghi, Editor(s)

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