Insulating Nanomagnets Driven by Spin Torque

Jungfleisch, M. Benjamin; Ding, J.; Zhang, Wei; Jiang, Wanjun; Pearson, John; Novosad, V.; Hoffmann, A.

doi:10.1021/acs.nanolett.6b02794

Cited by 30 publications

(13 citation statements)

References 37 publications

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“…For example, one can use the spin Hall effect of heavy metals to generate spin-orbit torques and drive the magnetization precession of an adjacent ferromagnet, known as the spin-torque ferromagnetic resonance (ST-FMR) [17], and then probe the ferromagnetic resonance (FMR) by electrical and optical means. In particular, the ferromagnet can be both metallic [17,19,20,22], or insulating [21,23,25,26] in this case owing to the decoupled charge current and pure spin current, which may offer additional advantages for energy efficiency.…”

Section: Introductionmentioning

confidence: 99%

Direct observation of spin accumulation in Cu induced by spin pumping

Ding

Zhang

Jungfleisch

et al. 2020

Phys. Rev. Research

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Pure spin currents have been ubiquitous in contemporary spintronics research. Despite its profound physical and technological significance, the detection of pure spin current has largely remained indirect, which is usually achieved by probing spin-transfer torque effects or spin-to-charge conversions. By using scanning transmission x-ray microscopy, we report the direct detection and spatial mapping of spin accumulation in a nonmagnetic Cu layer without any direct charge current injection. Such a pure spin current is induced by spin pumping from a Ni 80 Fe 20 layer and is not accompanied by concomitant charge motion. The observed frequency dependence indicates that the signal is dominated by a coherent, pure spin current, but the magnitude of the spin accumulation suggests also possible additional thermal contributions. Our technique takes advantage of the x-ray magnetic circular dichroism and the synchronization of microwave with x-ray pulses, which together provide a high sensitivity for probing transient magnetic moment. From the detected x-ray signals, we observe two distinct resonance modes induced by spin pumping, which, based on micromagnetic simulations, we attribute to nonlinear microwave excitations. Our result provides a new pathway for detecting pure spin currents that originate from many spintronics phenomena, such as spin Hall and spin Seebeck effects, and which can be applied to both metal and insulator spin current sources.

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Section: Introductionmentioning

confidence: 99%

Direct observation of spin accumulation in Cu induced by spin pumping

Ding

Zhang

Jungfleisch

et al. 2020

Phys. Rev. Research

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“…In addition, it is useful in the scenarios when electrical detection becomes technically challenging, such as for magnetic insulators where direct electrical modulation is unavailable [55][56][57], and in particular, when studying the spin-swapping, anomalous-Hall, and planar-Hall torques discovered recently in pure ferromagnets [58][59][60][61]. The stroboscopic method will also be in complementary to Brillouin light scattering [62] which measures inelastic light scattering by magnon-phonon, and X-ray magnetic circular dichroism [28,63,64].…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Optical and Electrical Spin-Torque Magnetometry with Phase-Sensitive Detection of Spin Precession

Sağlam

Zhang

et al. 2019

Phys. Rev. Applied

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Spin-based coherent information processing and encoding utilize the precession phase of spins in magnetic materials. However, the detection and manipulation of spin precession phases remain a major challenge for advanced spintronic functionalities. By using simultaneous electrical and optical detection, we demonstrate the direct measurement of the precession phase of Permalloy ferromagnetic resonance driven by the spin-orbit torques from adjacent heavy metals. The spin Hall angle of the heavy metals can be independently determined from concurrent electrical and optical signals. The stroboscopic optical detection also allows spatially measuring local spin-torque parameters and the induced ferromagnetic resonance with comprehensive amplitude and phase information. Our study offers a route towards future advanced characterizations of spin-torque oscillators, magnonic circuits, and tunnelling junctions, where measuring the current-induced spin dynamics of individual nanomagnets are required.Magneto-optical Kerr effect (MOKE) provides an alternative approach to "directly" access to the magnetization states. Both in-plane and out-of-plane magnetic moments can be detected [30] by the choice of different Kerr configurations. Recently, MOKE-based detection of electrically-induced SOTs have been reported [31][32][33][34], but only with quasi-static magnetization configurations, where the SOT is treated as an "effective field" that tilts the static magnetization of the FM. On the other hand, stroboscopic techniques [35][36][37][38][39], in which both the pump and probe are modulated at the dynamic excitation frequency, offer unique advantages in tracking both the amplitude and the phase information of the magnetization precession, and thus are more suitable in studying SOTdriven spin dynamics.Here, we report a simultaneous electrical and optical measurement of spin-torque ferromagnetic resonance (ST-FMR), with the capability to extract the spin precession phase driven by the SOTs. We show that the spin Hall angle of heavy metals can be directly extracted from the measured optical phase of spin dynamics, in-arXiv:1901.01923v1 [cond-mat.mes-hall]

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“…To overcome the challenge of a small coupling volume in magnetic nanostructures, one could replace the widely used metallic NiFe by materials with a larger spin density such as yttrium iron garnet (YIG). Indeed, recent progress showed that nanofabrication of YIG is feasible [496]. Moreover, this would enable the fabrication of arrays of nano-magnets [77] and magnonic crystals on planar resonators offering novel functionalities to tune the magnon resonance and propagation characteristics.…”

Section: G Planar Resonator-based Hybrid Magnonic Circuitsmentioning

confidence: 99%

Advances in Magnetics Roadmap on Spin-Wave Computing

et al. 2022

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Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.

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Insulating Nanomagnets Driven by Spin Torque

Cited by 30 publications

References 37 publications

Direct observation of spin accumulation in Cu induced by spin pumping

Direct observation of spin accumulation in Cu induced by spin pumping

Simultaneous Optical and Electrical Spin-Torque Magnetometry with Phase-Sensitive Detection of Spin Precession

Advances in Magnetics Roadmap on Spin-Wave Computing

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