Generation and Detection of Dresselhaus‐Like Spin Current in a Single‐Crystal Ferromagnetic Metal

Wang, Wentao; Yan, Ze; Cao, Yaoyao; Gao, Cunxu; Shi, Zhong; Si, Mingsu; Cao, Jiangwei; Xi, Li; Yang, Dezheng; Xue, Desheng

doi:10.1002/adfm.202204212

Cited by 6 publications

(9 citation statements)

References 44 publications

(62 reference statements)

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“…The sin2𝜑 signal is only 20% of that of the two-cross Hall-bar devices but still significant. As we comment in Section S1 of the Supporting Information, the sin2𝜑 signal in the previous study of CoFe samples [30] also varies significantly with the location of the cross on the three-cross Hall bar device, in agreement with the planar Nernst effect being the origin of the sin2𝜑 signals. Note that the presence of effects due to an unintentional symmetry imperfection is common in microscale strips and crosses.…”

Section: Origin Of the Sin2𝝋 Second Hhv Signalsupporting

confidence: 79%

“…We have presented unambiguous evidence that there is no sizable spin current generation from the bulk or interfaces of CoFe single crystal, even when the interface has very strong spin-orbit coupling (as in the case of the GaAs/CoFe sample). We verify that the sin2𝜑 second harmonic Hall voltage, which was previously assumed to signify the Dresselhaus-like spin current in the same materials, [30] is unrelated to any spin currents. Instead, it is the PNE voltage induced by the temperature gradient within the sample.…”

Section: Discussionsupporting

confidence: 60%

“…Therefore, the observation that the sin2𝜑 signal is much stronger for the MgO/CoFe than for the GaAs/CoFe strongly disagrees with the previous specula-tion that the sin2𝜑 second HHV signal arose from an interfacial SOC effect. [30] Finally, we show in Figure 5a,d that similar sin2𝜑 second HHV signals are also observed in control polycrystalline ferromagnetic layers of Py, Co, and FeCoB sputter-deposited on MgO-buffered Si/SiO 2 substrates, which is in contrary to an origin of a lowsymmetry interface of the CoFe single crystal. [30] Importantly, for all the samples studied in this work, the magnitude of V PNE scales closely with the planar Hall voltage (see Figure 5d,e, and Table 1).…”

Section: Origin Of the Sin2𝝋 Second Hhv Signalsupporting

confidence: 52%

“…Therefore, the observation that the sin2 φ signal is much stronger for the MgO/CoFe than for the GaAs/CoFe strongly disagrees with the previous speculation that the sin2 φ second HHV signal arose from an interfacial SOC effect. [ 30 ]…”

Section: Sample Details and Measurement Techniquesmentioning

confidence: 99%

“…Of particular surprise is a recent argument of longitudinal spins, Dresselhaus‐like spin current, from the interface of single‐crystalline CoFe samples based on a sin2 φ contribution in the second harmonic Hall voltage ( V 2ω ). [ 30 ] This is very stimulating particularly when there have been many other reports of exotic spin currents and SOTs within single crystals. [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] While the symmetry breaking that allows the longitudinal spins in that work [ 30 ] was attributed to the low‐symmetry point group of the single crystal but not clearly specified, there have been other reports that the anisotropic magnetoresistance (AMR) and magnetic damping in single‐crystalline CoFe vary with the crystalline orientation, [ 31 , 32 ] implying a possibility to generating low‐symmetry and anisotropic effects in the same material.…”

Section: Introductionmentioning

confidence: 99%

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Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

2023

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Exploration of exotic spin polarizations in single crystals is of increasing interest. A current of longitudinal spins, the so‐called “Dresselhaus‐like” spin current, which is forbidden in materials lacking certain inversion asymmetries, is implied to be generated by a charge current at the interface of single‐crystal CoFe. This work reports unambiguous evidence that there is no indication of spin current of any spin polarizations from the interface or bulk of single‐crystalline CoFe and that the sin2φ second harmonic Hall voltage, which is previously assumed to signify Dresselhaus‐like spin current, is not related to any spin currents but rather a planar Nernst voltage induced by a longitudinal temperature gradient within the sample. Such sin2φ signal is independent of large applied magnetic fields and interfacial spin‐orbit coupling, inversely correlated to the heat capacity of the substrates and overlayers, quadratic in charge current, and appears also in polycrystalline ferromagnets. Strikingly, the planar Nernst effect (PNE) in the CoFe single crystal has a strong fourfold anisotropy and varies with the crystalline orientation. Such strong, anisotropic PNE has widespread impacts on the analyses of a variety of spintronic experiments and opens a new avenue for the development of PNE‐based thermoelectric battery and sensor applications.

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Section: Origin Of the Sin2𝝋 Second Hhv Signalsupporting

confidence: 79%

Section: Discussionsupporting

confidence: 60%

Section: Origin Of the Sin2𝝋 Second Hhv Signalsupporting

confidence: 52%

Section: Sample Details and Measurement Techniquesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

2023

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Acoustic spin rotation in heavy-metal-ferromagnet bilayers

Cao,

Ding,

Zuo

et al. 2024

Nat Commun

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Through pumping a spin current from ferromagnet into heavy metal (HM) via magnetization precession, parts of the injected spins are in-plane rotated by the lattice vibration, namely acoustic spin rotation (ASR), which manifests itself as an inverse spin Hall voltage in HM with an additional 90° difference in angular dependency. When reversing the stacking order of bilayer with a counter-propagating spin current or using HMs with an opposite spin Hall angle, such ASR voltage shows the same sign, strongly suggesting that ASR changes the rotation direction due to interface spin-orbit interaction. With the drift-diffusion model of spin transport, we quantify the efficiency of ASR up to 30%. The finding of ASR endows the acoustic device with an ability to manipulate spin, and further reveals a new spin-orbit coupling between spin current and lattice vibration.

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Enhanced Spin–Orbit Torques in Graphene by Pt Adatoms Decoration

Wang 王,

Zhang 张,

Xu 徐

et al. 2024

Chinese Phys. Lett.

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Graphene (Gr) with widely acclaimed characteristics, such as exceptionally long spin diffusion length at room temperature, provides an outstanding platform for spintronics. However, its inherent weak spin-orbit coupling (SOC) has limited its efficiency for generating the spin currents in order to control the magnetization switching process for the application in spintronics memories. Following the theoretical prediction on the enhancement of SOC in Gr by heavy atoms adsorption, here we experimentally observe a sizeable spin-orbit torques (SOTs) in Gr by the decoration of its surface with Pt adatoms in Gr/Pt(t Pt )/FeNi trilayers with the optimal damping-like SOT efficiency around 0.55 by 0.6-nm-thick Pt layer adsorption. The value is nearly four times larger than that of the Pt/FeNi sample without Gr and nearly twice as large as that of the Gr/FeNi sample without Pt adsorption. The efficiency of the enhanced SOT in Gr by Pt adatoms is also demonstrated by the field-free SOT magnetization switching process with a relatively low critical current density around 5.4 MA/cm2 in Gr/Pt/FeNi trilayers with the in-plane magnetic anisotropy. These findings pave the way for Gr spintronics application, offering solutions for future low power consumption memories.

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Generation and Detection of Dresselhaus‐Like Spin Current in a Single‐Crystal Ferromagnetic Metal

Cited by 6 publications

References 44 publications

Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

Absence of Spin‐Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal

Acoustic spin rotation in heavy-metal-ferromagnet bilayers

Enhanced Spin–Orbit Torques in Graphene by Pt Adatoms Decoration

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