Giant antidamping orbital torque originating from the orbital Rashba-Edelstein effect in ferromagnetic heterostructures

Chen, Xi; Liu, Yang; Yang, Guang; Shi, Hui; Hu, Chen; Li, Minghua; Zeng, Haibo

doi:10.1038/s41467-018-05057-z

Cited by 48 publications

(33 citation statements)

References 54 publications

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“…These results may be related to the OT, which requires further investigation. Finally, we remark that the orbital angular momentum can be generated not only by the OHE but also by the interfacial Rashbatype states [36,37], which may be related to sizable field-like torque measured in Py/(Cu)/AlO x structure [38]. References S10…”

Section: Note That the Relative Ratio Between Smentioning

confidence: 99%

Orbital torque: Torque generation by orbital current injection

Lee

2020

Phys. Rev. Research

151

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We propose a mechanism of torque generation by injection of an orbital current, which we call orbital torque. In a magnetic bilayer consisting of a nonmagnet (NM) and a ferromagnet (FM), we consider a situation where the spin-orbit coupling (SOC) is present only in the FM. Although the SOC is absent in the NM, the orbital Hall effect can arise in the NM. When the resulting orbital Hall current is injected to the FM, the SOC of the FM converts the orbital angular momentum into spin, which exerts torque to the magnetization of the FM. Remarkably, even for small SOC strength comparable to that of 3d FMs, the orbital torque can be comparable to the spin torque induced by the spin Hall effect of the NM with strong SOC. This provides a way to experimentally probe the OHE and opens a new venue to achieving spin-torque devices based on light elements that exhibit gigantic orbital response. Experimental implications are discussed. * hwl@postech.ac.kr

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Section: Note That the Relative Ratio Between Smentioning

confidence: 99%

Orbital torque: Torque generation by orbital current injection

Lee

2020

Phys. Rev. Research

151

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“…On the other hand, in the case of Pt(O)/NiFe/SiO 2 with heavily oxidized Pt, the observed dominant DL SOT is attributed to an intrinsic SOT arising from the Berry curvature at the interface 23 . In addition to conventional REE, the combined effect of enhancement in orbital moment and spin-orbit coupling was also proposed to account for the sign reversal of DL SOT in Pt/CoFeB(O)/MgO below temperature of 200 K 20 , and significant enhancement in DL torque in Pt/Co/SiO 2 29 . The oxygen may also modify the charge and spin transport property at the interface, e.g ., it was reported that spin-mixing conductance of Co/CoO x /Pt is enhanced due to antiferromagnetic nature of CoO x 21,22 , and the spin Hall angle in Pt is increased by weakening of proximity effect 22 .…”

Section: Introductionmentioning

confidence: 99%

In-situ study of oxygen exposure effect on spin-orbit torque in Pt/Co bilayers in ultrahigh vacuum

Xie

Yuan

Luo

et al. 2019

Sci Rep

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Oxygen incorporation has been reported to increase the current-induced spin-orbit torque in ferromagnetic heterostructures, but the underlying mechanism is still under active debate. Here, we report on an in-situ study of the oxygen exposure effect on spin-orbit torque in Pt/Co bilayers via controlled oxygen exposure, Co and Mg deposition, and electrical measurements in ultrahigh vacuum. We show that the oxygen exposure on Pt/Co indeed leads to an increase of spin-orbit torque, but the enhancement is not as large as those reported previously. Similar enhancement of spin-orbit torque is also observed after the deposition of an MgO capping layer. The results of ab initio calculations on the Rashba splitting of Pt/Co and Pt/Co/O suggest that the enhancement is due to enhanced Rashba-Edelstein effect by surface-adsorbed oxygen. Our findings shed some light on the varying roles of oxygen in modifying the spin torque efficiency reported previously.

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“…In addition to the CISP, we study the polarization of the atomic orbital angular momentum, called the current-induced orbital polarization (CIOP), which acts on the spin as an effective magnetic field through the LS coupling. The CIOP was recently studied in crystals [70][71][72][73], and the orbital current was also calculated in the orbital Hall effect in crystals [74][75][76][77] and in the orbital filter in a model of CISS [78]. Here we calculate both CIOP and CISP as a function of the radius and the pitch of the helix in the linear response to the chemical-potential difference between source and drain electrodes in the Landauer approach.…”

Section: Introductionmentioning

confidence: 99%

Orbital and spin polarizations induced by current through a helical atomic chain

2021

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Current-induced spin and orbital polarizations are theoretically studied in a helical atomic chain with p x , p y , and p z orbitals in each atom in the linear response to the chemical-potential difference between source and drain electrodes. It is shown that these polarizations are parallel to the helix axis and proportional to the curvature of the cylinder surface defined by the helix in the small curvature region. This proportionality suggests that the curvature generates the coupling between the current and the atomic orbital angular momentum and therefore influences the magnitude of induced spin polarization through the LS coupling. It is also found that current-induced polarizations are nonzero even when the pitch is enforced to vanish. This suggests the possibility that nonchiral structures with curvature can produce current-induced polarizations. With this possibility in mind, it is proposed that the chirality in the current, rather than that in the structure, determines the existence of such current-induced polarizations.

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Giant antidamping orbital torque originating from the orbital Rashba-Edelstein effect in ferromagnetic heterostructures

Cited by 48 publications

References 54 publications

Orbital torque: Torque generation by orbital current injection

Orbital torque: Torque generation by orbital current injection

In-situ study of oxygen exposure effect on spin-orbit torque in Pt/Co bilayers in ultrahigh vacuum

Orbital and spin polarizations induced by current through a helical atomic chain

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