Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">W</mml:mi><mml:mo>/</mml:mo><mml:mi>CoFeB</mml:mi><mml:mo>/</mml:mo><mml:mi>MgO</mml:mi></mml:mrow></mml:math>
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Filianina, Mariia; Hanke, Jan-Philipp; Lee, Kyujoon; Han, Dong‐Soo; Jaiswal, Samridh; Rajan, Adithya; Jakob, G.; Mokrousov, Yuriy; Kläui, Mathias

doi:10.1103/physrevlett.124.217701

Cited by 55 publications

(26 citation statements)

References 43 publications

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“…After we have excluded non‐uniformities in magnetic moment density, electron scattering strength, and exchange stiffness as the dominant mechanisms of inversion asymmetry, the lattice strain gradient is left as the most likely symmetry‐breaking mechanism for the bulk dampinglike SOT. Microscopically, a strain gradient can non‐uniformly modify the strengths of the SHE, [ 31–35 ] spin‐orbit interaction, [ 36 ] orbital polarization, [ 37 ] spin states at the Fermi level, [ 37 ] and strain‐spin coupling, [ 38 ] ultimately leading to inversion symmetry breaking in the generation and relaxation of spin current within the sample. As shown in Figure 4c, the lattice constant of the chemically disordered Fe x Pt 1‐ x indeed increases by 2.3% as x from 0.25 to 0.75, [ 39 ] suggesting a very strong strain gradient in the composition‐gradient samples.…”

Section: Resultsmentioning

confidence: 99%

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers

Zhu

Ralph

Buhrman

2021

Adv Funct Materials

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The recent discovery of spin‐orbit torques (SOTs) within magnetic single‐layers has attracted attention. However, it remains elusive as to how to understand and how to tune the SOTs. Here, utilizing the single layers of chemically disordered FexPt1‐x, the mechanism of the “unexpected” bulk SOTs is unveiled by studying their dependence on the introduction of a controlled vertical composition gradient and temperature. The bulk dampinglike SOT is found to arise from an imbalanced internal spin current that is transversely polarized and independent of the magnetization orientation. The torque can be strong only in the presence of a vertical composition gradient. The SOT efficiency per electric field is insensitive to temperature but changes sign upon reversal of the orientation of the composition gradient, which is analog to the strain behaviors. These characteristics suggest that the imbalanced internal spin current originates from a bulk spin Hall effect and that the associated inversion asymmetry that allows for a non‐zero net torque is most likely a strain non‐uniformity induced by the composition gradient. The fieldlike SOT is a relatively small bulk effect compared to the dampinglike SOT. This study points to the possibility of developing low‐power single‐layer SOT devices by strain engineering.

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Section: Resultsmentioning

confidence: 99%

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers

Zhu

Ralph

Buhrman

2021

Adv Funct Materials

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“…To date, the behavior of a transverse spin current at the FMI / HM interface has not been fully understood, but it is of key importance, as it governs the SOT induced switching of any FMI. The second main ingredient for the magnetic switching, via domain wall motion induced by SOT, is the Dzyaloshinskii-Moriya interaction (DMI), which also results from spin-orbit coupling effects [12,13]. Often, a sizeable DMI is found in systems where SOT are observed, and the DMI stabilizes chiral spin structures such as skyrmions and chiral domain walls [14], which can then be efficiently manipulated by SOT [15,16].…”

mentioning

confidence: 99%

Identifying the origin of the nonmonotonic thickness dependence of spin-orbit torque and interfacial Dzyaloshinskii-Moriya interaction in a ferrimagnetic insulator heterostructure

et al. 2020

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Electrical manipulation of magnetism via spin-orbit torques (SOTs) promises efficient spintronic devices. In systems comprising magnetic insulators and heavy metals, SOTs have started to be investigated only recently, especially in systems with interfacial Dzyaloshinskii-Moriya interaction (iDMI). Here, we quantitatively study the SOT efficiency and iDMI in a series of gadolinium gallium garnet (GGG) / thulium iron garnet (TmIG) / platinum (Pt) heterostructures with varying TmIG and Pt thicknesses. We find that the non-monotonic SOT efficiency as a function of the magnetic layer thickness is not consistent with the 1/thickness dependence expected from a simple interfacial SOT mechanism. Moreover, considering the insulating nature of TmIG, our results cannot be explained by the SOT mechanism established for metallic magnets where the transverse charge spin current can 2 inject and dephase in the magnetic layers. Rather we can explain this non-monotonic behavior by a model based on the interfacial spin mixing conductance that is affected by the thickness-dependent exchange splitting energy by determining the phase difference of the reflected spin-up and spin-down electrons at the TmIG / Pt interface. By studying the Pt thickness dependence, we find that the effective DMI for GGG / TmIG / Pt does not depend on the Pt thickness, which indicates that the GGG / TmIG interface is the source of the iDMI in this system. Our work demonstrates that SOT and DMI can originate from two different interfaces, which enables independent optimization of DMI and SOT for advanced chiral spintronics with low damping magnetic insulators.

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“…The increasing SOT ratio with gate-voltage could be explained by an increased carrier density leading to an enhanced current at the WS 2 /Py interface. The modulation of SOT strength using a gate voltage is a step toward applications for data storage and processing and more research should be done to improve the gate tunability of SOTs in TMD/FM heterostructures (Li et al, 2020;Filianina et al, 2020;Dieny et al, 2019).…”

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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Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized W/CoFeB/MgO Films

Cited by 55 publications

References 43 publications

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers

Identifying the origin of the nonmonotonic thickness dependence of spin-orbit torque and interfacial Dzyaloshinskii-Moriya interaction in a ferrimagnetic insulator heterostructure

Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures

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Electric-Field Control of Spin-Orbit Torques in Perpendicularly Magnetized W/CoFeB/MgO Films

Cited by 55 publications

References 43 publications

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered FexPt1‐x Single Layers

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered FexPt1‐x Single Layers

Identifying the origin of the nonmonotonic thickness dependence of spin-orbit torque and interfacial Dzyaloshinskii-Moriya interaction in a ferrimagnetic insulator heterostructure

Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures

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Product

Resources

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Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers

Unveiling the Mechanism of Bulk Spin‐Orbit Torques within Chemically Disordered Fe_xPt_1‐_x Single Layers