title: Controlling the competition between optically induced ultrafast spin-flip scattering and spin transport in magnetic multilayers.
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.
authors.affiliation: Department of Physics and JILA, University of Colorado, Boulder and NIST, Colorado 80309, USA.
authors.forename: Emrah
authors.initials: E
authors.lastname: Turgut
authors.forename: Chan
authors.initials: C
authors.lastname: La-o-Vorakiat
authors.forename: Justin M
authors.initials: JM
authors.lastname: Shaw
authors.forename: Patrik
authors.initials: P
authors.lastname: Grychtol
authors.forename: Hans T
authors.initials: HT
authors.lastname: Nembach
authors.forename: Dennis
authors.initials: D
authors.lastname: Rudolf
authors.forename: Roman
authors.initials: R
authors.lastname: Adam
authors.forename: Martin
authors.initials: M
authors.lastname: Aeschlimann
authors.forename: Claus M
authors.initials: CM
authors.lastname: Schneider
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Silva
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.forename: Stefan
authors.initials: S
authors.lastname: Mathias