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Controlling the competition between optically induced ultrafast spin-flip scattering and spin transport in magnetic multilayers.

Research paper by Emrah E Turgut, Chan C La-o-Vorakiat, Justin M JM Shaw, Patrik P Grychtol, Hans T HT Nembach, Dennis D Rudolf, Roman R Adam, Martin M Aeschlimann, Claus M CM Schneider, Thomas J TJ Silva, Margaret M MM Murnane, Henry C HC Kapteyn, Stefan S Mathias

Indexed on: 28 May '13Published on: 28 May '13Published in: Physical review letters



Abstract

The study of ultrafast dynamics in magnetic materials provides rich opportunities for greater fundamental understanding of correlated phenomena in solid-state matter, because many of the basic microscopic mechanisms involved are as-yet unclear and are still being uncovered. Recently, two different possible mechanisms have been proposed to explain ultrafast laser induced magnetization dynamics: spin currents and spin-flip scattering. In this work, we use multilayers of Fe and Ni with different metals and insulators as the spacer material to conclusively show that spin currents can have a significant contribution to optically induced magnetization dynamics, in addition to spin-flip scattering processes. Moreover, we can control the competition between these two processes, and in some cases completely suppress interlayer spin currents as a sample undergoes rapid demagnetization. Finally, by reversing the order of the Fe/Ni layers, we experimentally show that spin currents are directional in our samples, predominantly flowing from the top to the bottom layer.