title: Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current.
abstract: Uncovering the physical mechanisms that govern ultrafast charge and spin dynamics is crucial for understanding correlated matter as well as the fundamental limits of ultrafast spin-based electronics. Spin dynamics in magnetic materials can be driven by ultrashort light pulses, resulting in a transient drop in magnetization within a few hundred femtoseconds. However, a full understanding of femtosecond spin dynamics remains elusive. Here we spatially separate the spin dynamics using Ni/Ru/Fe magnetic trilayers, where the Ni and Fe layers can be ferro- or antiferromagnetically coupled. By exciting the layers with a laser pulse and probing the magnetization response simultaneously but separately in Ni and Fe, we surprisingly find that optically induced demagnetization of the Ni layer transiently enhances the magnetization of the Fe layer when the two layer magnetizations are initially aligned parallel. Our observations are explained by a laser-generated superdiffusive spin current between the layers.
authors.affiliation: Peter Grünberg Institut PGI-6 & JARA-FIT, Research Centre Jülich, 52425 Jülich, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Rudolf
authors.forename: Chan
authors.initials: C
authors.lastname: La-O-Vorakiat
authors.forename: Marco
authors.initials: M
authors.lastname: Battiato
authors.forename: Roman
authors.initials: R
authors.lastname: Adam
authors.forename: Justin M
authors.initials: JM
authors.lastname: Shaw
authors.forename: Emrah
authors.initials: E
authors.lastname: Turgut
authors.forename: Pablo
authors.initials: P
authors.lastname: Maldonado
authors.forename: Stefan
authors.initials: S
authors.lastname: Mathias
authors.forename: Patrik
authors.initials: P
authors.lastname: Grychtol
authors.forename: Hans T
authors.initials: HT
authors.lastname: Nembach
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Silva
authors.forename: Martin
authors.initials: M
authors.lastname: Aeschlimann
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.forename: Claus M
authors.initials: CM
authors.lastname: Schneider
authors.forename: Peter M
authors.initials: PM
authors.lastname: Oppeneer