Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque

Aoki, Motomi; Shigematsu, Ei; Ohshima, Ryo; Shinjo, Teruya; Shiraishi, Masashi; Ando, Yoshinori

doi:10.1103/physrevb.106.174418

Cited by 8 publications

(3 citation statements)

References 52 publications

(45 reference statements)

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“…In addition, in HM/FM bilayers, the self-torque in the FM layers could counteract the torque generated by the HM layer, resulting in a reduced net torque. Taking advantage of the self-torques in the FM layer, making them work in conjunction with other SOTs instead, could lead to an increase in the SOT efficiency [3]. Tailoring the FM interfaces to change the self-torque direction and strength, in conjunction with searching for different materials as SOT sources, could be a promising route towards an increase in SOT efficiency.…”

Section: Discussionmentioning

confidence: 99%

“…Also, electrical measurements on Py capped with SiO 2 or Al 2 O 3 show the presence of field-like and damping-like torques in Py devices [37]. And in metallic bilayers, it was shown that self-induced torques lead to errors in the estimation of the spin-torque strength [3]. These self-torques in ferromagnetic materials make it difficult to accurately determine to what extent the TMD layer is contributing to the SOT [37].…”

Section: Introductionmentioning

confidence: 99%

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The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

Hidding¹,

Mërtiri²,

Mujid³

et al. 2023

Preprint

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In recent years, transition metal dichalcogenides (TMDs) have been extensively studied for their efficient spin-orbit torque generation in TMD/ferromagnetic bilayers, owing to their large spin-orbit coupling, large variety of crystal symmetries, and pristine interfaces. Although the TMD layer was considered essential for the generation of the observed SOTs, recent reports show the presence of a self-torque in single-layer ferromagnetic devices with magnitudes comparable to TMD/ferromagnetic devices. Here, we perform second-harmonic Hall SOT measurements on metal-organic chemical vapor deposition (MOCVD) grown MoS2/permalloy/Al2O3 devices and compare them to a singlelayer permalloy/Al2O3 device to accurately disentangle the role of self-torques, arising from the ferromagnetic layer, from contributions from the TMD layer in these bilayers. We report a dampinglike self-torque of σDL = (−2.5 ± 0.6) × 10 5 2e (Ω • m) −1 in our single-layer permalloy/Al2O3 device, while we observe a weaker σDL with opposite sign in one MoS2/permalloy/Al2O3 device, and no significant σDL for all other MoS2/permalloy/Al2O3 devices. The opposite sign of these torques indicates a competition between the self-torque and the torque arising from the TMD layer, which would reduce the observed torque in these bilayers. In addition, we find a field-like spin-torque conductivity of σF L = (−2.8 ± 0.3) × 10 3 2e (Ω • m) −1 in a single-layer permalloy/Al2O3 device, which is comparable to control MoS2/permalloy/Al2O3 devices and previous reports on similar TMD/FM bilayers, indicating only a minor role of the MoS2 layer. Finally, we find a linear dependence of the SOT conductivity on the Hall bar leg/channel width ratio of our devices, indicating that the Hall bar dimensions are of significant importance for the reported SOT strength. Our results accentuate the importance of delicate details, like device asymmetry, Hall bar dimensions, and selftorque generation, for the correct disentanglement of the microscopic origins underlying the SOTs, essential for future energy-efficient spintronic applications.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

Hidding¹,

Mërtiri²,

Mujid³

et al. 2023

Preprint

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“…Regarding the SOT, spin current generated by the spin Hall effect (SHE) in the bulk of nonmagnetic metals, due to interface SOI (ISOI) and/or topological surface states, flows into an adjacent ferromagnetic material (FM), resulting in magnetization reversal. SOT has been demonstrated in a variety of systems, such as heavy metal/FM, , topological insulator/FM, , 2D material heterostructures, and even single FM layers without adjacent materials, , the latter referred to as self-induced SOT (SI-SOT). Despite the significant potential of SOT, its practical application in spintronic devices such as nonvolatile memory devices, oscillators, and domain-wall memories is still limited by the challenge of controlling its magnitude and orientation.…”

mentioning

confidence: 99%

Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co₂MnGa

et al. 2023

Self Cite

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Spin-orbit torque (SOT) is receiving tremendous attention from both fundamental and application-oriented aspects. Co2MnGa, a Weyl ferromagnet that is in a class of topological quantum materials, possesses cubic-based high structural symmetry, the L21 crystal ordering, which should be incapable of hosting anisotropic SOT in conventional understanding. Here we show the discovery of a gigantic anisotropy of self-induced SOT in Co2MnGa. The magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer systems, despite the high inversion symmetry of the Co2MnGa structure. More surprisingly, a sign inversion of the self-induced SOT is observed for different crystal axes. This finding stems from the interplay of the topological nature of the electronic states and their strong modulation by external strain. Our research enriches the understanding of the physics of self-induced SOT and demonstrates a versatile method for tuning SOT efficiencies in a wide range of materials for topological and spintronic devices.

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Spin current and spin-orbit torque induced by ferromagnets

Kim,

Park,

Lee

2024

npj Spintronics

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Spin torque is typically classified based on how the spin current is generated and injected into a magnet for manipulation. Spin-orbit torque arises from the spin-orbit interaction in a nearby normal metal, while spin-transfer torque results from exchange interactions in another ferromagnet. Recent studies have suggested that a ferromagnet itself can also generate a spin current through spin-orbit coupling, leading to the emergence of ferromagnet-induced spin-orbit torque as another class of spin torque. This novel torque mechanism not only inherits the advantages of spin-orbit torque architectures, such as separate reading and writing paths in memory applications but also offers the flexibility to control the generated spin direction by manipulating the orientation of the ferromagnet responsible for generating the spin current. In this article, we review the phenomena related to spin currents generated by ferromagnets, explore their physical descriptions in heterostructures, and discuss several spin torque architectures based on this effect. Ferromagnet-induced spin-orbit torque not only introduces new physical consequences by combining spin-orbit and exchange interactions but also offers a promising building block in spintronics with significant potential for diverse applications.

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Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque

Cited by 8 publications

References 52 publications

The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co₂MnGa

Spin current and spin-orbit torque induced by ferromagnets

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Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque

Cited by 8 publications

References 52 publications

The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

The Role of Self-Torques in Transition Metal Dichalcogenide/Ferromagnet Bilayers

Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co2MnGa

Spin current and spin-orbit torque induced by ferromagnets

Contact Info

Product

Resources

About

Gigantic Anisotropy of Self-Induced Spin-Orbit Torque in Weyl Ferromagnet Co₂MnGa