Interface-induced field-like optical spin torque in a ferromagnet/heavy metal heterostructure

Iihama, Satoshi; Ishibashi, Kazuaki; Mizukami, Shigemi

doi:10.1515/nanoph-2020-0571

Cited by 7 publications

(3 citation statements)

References 65 publications

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“…Subsequently, the flow of electron-SAM is converted to charge current through the inverse spin-Hall effect. Although photon-SAM driven torques were observed in heavy metal/ferromagnet bilayer films via timeresolved magneto-optical Kerr effect measurement [2,[19][20][21], the abovementioned HD photocurrent in a single thin film has been mostly reported in Bi-related materials [16,17,22]. Therefore, the efficient photo-spin conversion effect in Bi is expected, which most likely originates from the band structure inherent to semi-metallic Bi.…”

Section: Introductionmentioning

confidence: 99%

Different spin relaxation property observed in linearly and circularly polarized laser induced terahertz emission from Bi/Co bilayer

Ishibashi¹,

Iihama²,

Mizukami³

2023

Preprint

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Recently, helicity-dependent photocurrent was reported in Bi single thin films. It is proposed that the origin of this photocurrent is the combination of photo-spin conversion and spin-charge conversion effects in Bi and efficient spin conversion in Bi is expected. In this study, we measured two types of terahertz (THz) emissions from Bi/Co bilayer films induced by spin current generation using laser-induced demagnetization of the Co layer and photo-spin conversion effect in the Bi layer to investigate the spin current induced by the two mechanisms simultaneously. We clearly observed different Bi thickness dependence of peak intensity and that of bandwidth for THz spin current in two experiments, i.e., spin current induced by demagnetization of Co and that by photo-spin conversion in Bi. The different Bi thickness dependence of spin current intensity and bandwidth in two experiments is caused by different spin relaxation properties of optically excited spin currents in Bi layers.

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Section: Introductionmentioning

confidence: 99%

Different spin relaxation property observed in linearly and circularly polarized laser induced terahertz emission from Bi/Co bilayer

Ishibashi¹,

Iihama²,

Mizukami³

2023

Preprint

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“…[12][13][14] In particular, spin transfer torque (STT) was induced through subpicosecond laser-driven spin currents, [14] and optical spin torque through circularly polarized pump pulses has been demonstrated at heavy metal-ferromagnet interfaces. [15,16] We aim to show the way to determine and increase the spin injection efficiency such that future ultrafast spintronics applications become possible, through generating microscopic insight by a combination of time-resolved experiment and ab initio theory.Crucially, the non-equilibrium spin injection is concentrated in a sub-100 fs pulse and thus generates a transient spin current with high peak intensity. Since the non-equilibrium spin injection is induced by optical excitation and consists of a spin-dependent charge current, not only states near the Fermi level are involved, but those in a several eV wide energetic region around it, as given by the photon energy of the pump laser pulse.…”

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confidence: 99%

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confidence: 99%

Transient Spin Injection Efficiencies at Ferromagnet–Metal Interfaces

Elliott¹,

Eschenlohr²,

Chen³

et al. 2022

Adv Materials Inter

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Spin injection across interfaces driven by ultrashort optical pulses on femtosecond timescales constitutes a new way to design spintronics applications. Targeted utilization of this phenomenon requires knowledge of the efficiency of non‐equilibrium spin injection. From a quantitative comparison of ab initio time‐dependent density functional theory and interface‐sensitive, time‐resolved non‐linear optical experiment, the spin injection efficiency (SIE) at the Co/Cu(001) interface is determined, and its microscopic origin, i.e., the influence of spin‐orbit coupling and the interface electronic structure, is discussed. Moreover, we theoretically predict that the SIE at ferromagnetic–metal interfaces can be optimized through laser pulse and materials parameters, namely the fluence, pulse duration, and substrate material.

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Photon Energy‐Dependent Optical Spin‐Orbit Torque in Heavy Metal–Ferromagnet Bilayers

Wang,

Xu,

Liu

2023

Adv Funct Materials

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The manipulation of magnetization through optically generated ultrafast spin currents is a fascinating area that needs a thorough understanding for its potential future applications. In this work, a comprehensive investigation of helicity‐driven optical spin‐orbit torque in heavy metal/ferromagnetic metal heterostructures is presented, specifically cobalt capped with gold or platinum, subject to laser pumping at different wavelengths. The results demonstrate up to tenfold enhancement in optical spin‐orbit torque quantum efficiency for gold compared to platinum of the same thickness when pumped with a visible laser. Additionally, the study provides the first experimental analysis of the photon energy dependence of optical spin‐orbit torque and derives the optical spin orientation spectra for both gold/cobalt and platinum/cobalt heterostructures. A key insight gained from the study is the impact of photon energy‐dependent spin transport in the system, which suggests the use of a high photon energy pump for efficient spin transport. These findings highlight the potential of spin current generation and manipulation in gold/ferromagnet heterostructures for a wide range of applications such as all‐optical magnetization switching, spin‐wave generation and control, and spintronic terahertz emission.

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Interface-induced field-like optical spin torque in a ferromagnet/heavy metal heterostructure

Cited by 7 publications

References 65 publications

Different spin relaxation property observed in linearly and circularly polarized laser induced terahertz emission from Bi/Co bilayer

Different spin relaxation property observed in linearly and circularly polarized laser induced terahertz emission from Bi/Co bilayer

Transient Spin Injection Efficiencies at Ferromagnet–Metal Interfaces

Photon Energy‐Dependent Optical Spin‐Orbit Torque in Heavy Metal–Ferromagnet Bilayers

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