Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

Berger, Andrew; Edwards, Eric R. J.; Nembach, Hans T.; Karenowska, A. D.; Weiler, Mathias; Silva, Thomas J.

doi:10.1103/physrevb.97.094407

Cited by 44 publications

(69 citation statements)

References 51 publications

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“…From the Py thickness series we focus on three quantities: (1) the FM contribution to the sample inductance (L FM , as in Ref. 25), (2) the effective magnetization M eff , and (3) the Gilbert damping parameter α. From L FM as a function of Py thickness ( Fig.…”

Section: A Py Thickness Seriesmentioning

confidence: 99%

Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements

et al. 2018

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Understanding the evolution of spin-orbit torque (SOT) with increasing heavy-metal thickness in ferromagnet/normal metal (FM/NM) bilayers is critical for the development of magnetic memory based on SOT. However, several experiments have revealed an apparent discrepancy between damping enhancement and damping-like SOT regarding their dependence on NM thickness. Here, using linewidth and phase-resolved amplitude analysis of vector network analyzer ferromagnetic resonance (VNA-FMR) measurements, we simultaneously extract damping enhancement and both field-like and damping-like inverse SOT in Ni 80 Fe 20 /Pt bilayers as a function of Pt thickness. By enforcing an interpretation of the data which satisfies Onsager reciprocity, we find that both the damping enhancement and damping-like inverse SOT can be described by a single spin diffusion length (≈ 4 nm), and that we can separate the spin pumping and spin memory loss contributions to the total damping. This analysis indicates that less than 40% of the angular momentum pumped by FMR through the Ni 80 Fe 20 /Pt interface is transported as spin current into the Pt. On account of the spin memory loss and corresponding reduction in total spin current available for spin-charge transduction in the Pt, we determine the Pt spin Hall conductivity (σ SH = (2.36 ± 0.04) × 10 6 Ω −1 m −1 ) and bulk spin Hall angle (θ SH = 0.387 ± 0.008) to be larger than commonly-cited values. These results suggest that Pt can be an extremely useful source of SOT if the FM/NM interface can be engineered to minimize spin loss. Lastly, we find that self-consistent fitting of the damping and SOT data is best achieved by a model with Elliott-Yafet spin relaxation and extrinsic inverse spin Hall effect, such that both the spin diffusion length and spin Hall conductivity are proportional to the Pt charge conductivity. * thomas.silva@nist.gov † Contribution of the National Institute of Standards and Technology; not subject to copyright.

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Section: A Py Thickness Seriesmentioning

confidence: 99%

Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements

et al. 2018

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“…The linewidth of the t = 26 nm thick sample is shown in Fig. 2 (c) on an expanded scale.to Ref 21. of the radiative damping is done by analyzing the magnitude of the measured inductance L of all samples.…”

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confidence: 99%

High spin-wave propagation length consistent with low damping in a metallic ferromagnet

Flacke

Liensberger

Althammer

et al. 2019

Applied Physics Letters

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We report ultra-low intrinsic magnetic damping in Co 25 Fe 75 heterostructures, reaching the low 10 −4 regime at room temperature. By using a broadband ferromagnetic resonance technique in out-of-plane geometry, we extracted the dynamic magnetic properties of several Co 25 Fe 75 -based heterostructures with varying ferromagnetic layer thickness. By measuring radiative damping and spin pumping effects, we found the intrinsic damping of a 26 nm thick sample to be α 0 3.18 × 10 −4 . Furthermore, using Brillouin light scattering microscopy we measured spin-wave propagation lengths of up to (21 ± 1) µm in a 26 nm thick Co 25 Fe 75 heterostructure at room temperature, which is in excellent agreement with the measured damping.Itinerant ferromagnets (FM) are advantageous for spintronic and magnonic devices. They benefit from, e.g., large magnetoresistive effects and current-induced spinorbit torques 1 . In many magneto-resistive technologies (e.g., anisotropic magnetoresistance, giant magnetoresistance, tunnel magnetoresistance) electronic conductivity is indispensable. Moreover, due to high saturation magnetization in metallic FMs, spin-wave (SW) group velocities are in general significantly higher than in insulating ferrimagnets 2-5 . High saturation magnetizations in general ease detection. Nevertheless, itinerant FMs typically have considerable magnetic damping 6,7 . This is unfavorable for many applications. For example, low damping is crucial for oscillators based on spin transfer torques and spin orbit torques as well as for achieving large spin-wave propagation lengths (SWPL) 8-10 . The need for thin film materials with low magnetic damping has triggered the interest in the insulating ferrimagnet yttrium-iron garnet (Y 3 Fe 5 O 12 , YIG) 11-13 . Although for YIG, very small total (Gilbert) damping parameters in the order of α G ≈ 10 −5 , and large SWPLs of a few tens of micrometers (up to ∼ 25 µm) in thin films (∼ 20 nm) have been reported 5,13,14 , its insulating properties and requirement for crystalline growth are challenges for large scale magnonic applications.Schoen et al. recently observed ultra-low intrinsic magnetic damping in Co 25 Fe 75 (CoFe) metallic thin films (α 0 = (5 ± 1.8) × 10 −4 ) 15 , and Krner et al. reported PLs of 5 µm − 8 µm in CoFe using time resolved scanning magneto-optical Kerr microscopy 4 . This motivated our study on sputter-deposited CoFe-based thin film heterostructures. We use broadband ferromagnetic resonance (BB-FMR) spectroscopy 16 in outa) Electronic of-plane (OOP) geometry and Brillouin light scattering (BLS) microscopy 17 and find intrinsic damping parameters in the lower 10 −4 regime as well as SWPLs of more than 20 µm. The damping is therefore comparable to YIG/heavy metal (HM) heterostructures 18 and the SWPL is comparable to that of state-of-the-art YIG thin films 5,13 . Thin film CoFe is a promising candidate for all-metal magnonic devices, as it combines low magnetic damping with good electrical conductivity and large saturation magnetization, while enabling easy fab...

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“…The field of SOTs using TMD-based devices has been rapidly developed in the past 5 years. Experimental studies have used different TMD sources (e.g., mechanical exfoliation or chemical vapor deposition, CVD), FM materials, deposition methods (e.g., sputtering or electron-beam evaporation), and measurement techniques, namely second-harmonic Hall (SHH) (Garello et al, 2013;Hayashi et al, 2014;Avci et al, 2014;Ghosh et al, 2017) or spin-torque ferromagnetic resonance (ST-FMR) (Liu et al, 2011;Fang et al, 2011;Berger et al, 2018). So far, it is unclear how these different techniques and procedures affect the measured SOTs.…”

Section: Discussion On Recent Progressmentioning

confidence: 99%

Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures

Hidding

Guimarães

2020

Front. Mater.

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In recent years, there has been a growing interest in spin-orbit torques (SOTs) for manipulating the magnetization in nonvolatile magnetic memory devices. SOTs rely on the spin-orbit coupling of a nonmagnetic material coupled to a ferromagnetic layer to convert an applied charge current into a torque on the magnetization of the ferromagnet (FM). Transition metal dichalcogenides (TMDs) are promising candidates for generating these torques with both high charge-to-spin conversion ratios, and symmetries and directions which are efficient for magnetization manipulation. Moreover, TMDs offer a wide range of attractive properties, such as large spin-orbit coupling, high crystalline quality and diverse crystalline symmetries. Although numerous studies were published on SOTs using TMD/FM heterostructures, we lack clear understanding of the observed SOT symmetries, directions, and strengths. In order to shine some light on the differences and similarities among the works in literature, in this mini-review we compare the results for various TMD/FM devices, highlighting the experimental techniques used to fabricate the devices and to quantify the SOTs, discussing their potential effect on the interface quality and resulting SOTs. This enables us to both identify the impact of particular fabrication steps on the observed SOT symmetries and directions, and give suggestions for their underlying microscopic mechanisms. Furthermore, we highlight recent progress of the theoretical work on SOTs using TMD heterostructures and propose future research directions.

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Inductive detection of fieldlike and dampinglike ac inverse spin-orbit torques in ferromagnet/normal-metal bilayers

Cited by 44 publications

References 51 publications

Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements

Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements

High spin-wave propagation length consistent with low damping in a metallic ferromagnet

Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures

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