Ultrafast Laser-Excited Spin Transport in Au/Fe/MgO(001): Relevance of the Fe Layer Thickness

Alekhin, Alexandr; Bürstel, Damian; Melnikov, Alexey; Diesing, Detlef; Bovensiepen, Uwe

doi:10.1007/978-3-319-07743-7_75

Cited by 8 publications

(4 citation statements)

References 3 publications

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“…Also, it implies that the full thickness of the OOP layer contributes to the generated spin current. The latter notion contradicts the idea of a limited interface region (≈1 nm) contributing to the spin current generation, as was suggested by Alekhin et al for Fe/Au [13]. In the case of a superdiffusive spin current, the spin current is generated due to spin filtering of the hot electrons in the magnetic layer [5].…”

Section: B Spin Current Generationmentioning

confidence: 83%

“…This was first demonstrated in a collinear magnetic bilayer, where angular momentum transfer through the spacer layer resulted in a faster and larger demagnetization of the two antiparallel FM layers [10]. Several more recent studies have confirmed these laser-pulse induced spin currents [11][12][13][14][15][16]. It has even been claimed that the optically excited spin current can enhance the magnetization in one of the FM layers of the magnetic bilayer [12].…”

Section: Introductionmentioning

confidence: 84%

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Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Lalieu

Koopmans

2017

Phys. Rev. B

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Spin currents can be generated on an ultrafast time scale by excitation of a ferromagnetic (FM) thin film with a femtosecond laser pulse. Recently, it has been demonstrated that these ultrafast spin currents can transport angular momentum to neighboring FM layers, being able to change both the magnitude and orientation of the magnetization in the adjacent layer. In this paper, both the generation and absorption of these optically excited spin currents are investigated. This is done using noncollinear magnetic bilayers, i.e., two FM layers separated by a conductive spacer. Spin currents are generated in a Co/Ni multilayer with out-of-plane (OOP) anisotropy, and absorbed by a Co layer with an in-plane (IP) anisotropy. This behavior is confirmed by careful analysis of the laser-pulse induced magnetization dynamics, whereafter it is demonstrated that the transverse spin current is absorbed very locally near the injection interface of the IP layer (90% within the first ≈2 nm). Moreover, it will also be shown that this local absorption results in the excitation of THz standing spin waves within the IP layer. The dispersion measured for these high-frequency spin waves shows a discrepancy with respect to the theoretical predictions, for which an explanation involving intermixed interface regions is proposed. Lastly, the spin current generation is investigated by using magnetic bilayers with a different number of repeats for the Co/Ni multilayer, which proves to be of great relevance for identifying the optical spin current generation mechanism.

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Section: B Spin Current Generationmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 84%

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Lalieu

Koopmans

2017

Phys. Rev. B

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“…Ballistic Fe spins injected into a Au layer travelling close to the Au Fermi velocity arrive at the Au back interface within hundreds of femtoseconds while a diffusive component was detected at times up to 1 ps, in qualitative agreement with wave diffusion calculations [Kaltenborn et al ., 2012]. Variation of Fe layer thickness shows that the active injection region is an ≈1 nm thick Fe layer at the Fe/Au interface [Melnikov et al ., 2011; Alekhin et al ., 2015; Melnikov et al ., 2015], implying that superdiffusive transport is of limited importance for ultrafast demagnetization of significantly thicker ferromagnetic films, an observation supported by recent demagnetization experiments in Ni films [Schellekens et al ., 2013]. [Ando et al ., 2011; Hoffmann, 2013] used the inverse spin Hall effect to detect superdiffusive spin currents in non-magnetic layers.…”

Section: Interfacial Effects In Ultrafast Magnetization Dynamicsmentioning

confidence: 99%

Interface-induced phenomena in magnetism

et al. 2017

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This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.

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“…Some experiments suggest different ways as to how the superdiffusive spin current generation is distributed along the multilayer, especial along FM1. Alekhin et al [57] deduce that in a layer consisting of Fe/Au films just a very thin interfacial region (around 1 nm) contributes to the spin current generation. On the other hand, Lalieu et al [35] show that, at least in a small range of thicknesses, almost the whole out-of-plane magnetized layer, consisting of Co/Ni thin films, is used for SC generation.…”

Section: Generation Of the Spin Currentmentioning

confidence: 99%

Transport theory for femtosecond laser-induced spin-transfer torques

Baláž

Žonda

Carva

et al. 2018

J. Phys.: Condens. Matter

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Ultrafast demagnetization of magnetic layers pumped by a femtosecond laser pulse is accompanied by a nonthermal spin-polarized current of hot electrons. These spin currents are studied here theoretically in a spin valve with noncollinear magnetizations. To this end, we introduce an extended model of superdiffusive spin transport that enables the treatment of noncollinear magnetic configurations, and apply it to the perpendicular spin valve geometry. We show how spin-transfer torques arise due to this mechanism and calculate their action on the magnetization present, as well as how the latter depends on the thicknesses of the layers and other transport parameters. We demonstrate that there exists a certain optimum thickness of the out-of-plane magnetized spin-current polarizer such that the torque acting on the second magnetic layer is maximal. Moreover, we study the magnetization dynamics excited by the superdiffusive spin-transfer torque due to the flow of hot electrons employing the Landau-Lifshitz-Gilbert equation. Thereby we show that a femtosecond laser pulse applied to one magnetic layer can excite small-angle precessions of the magnetization in the second magnetic layer. We compare our calculations with recent experimental results.

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Ultrafast Laser-Excited Spin Transport in Au/Fe/MgO(001): Relevance of the Fe Layer Thickness

Cited by 8 publications

References 3 publications

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Absorption and generation of femtosecond laser-pulse excited spin currents in noncollinear magnetic bilayers

Interface-induced phenomena in magnetism

Transport theory for femtosecond laser-induced spin-transfer torques

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