Current-induced torques and interfacial spin-orbit coupling

Haney, Paul M.; Lee, Hyun Woo; Lee, Kyung Jin; Manchon, Aurélien; Stiles, Mark D.

doi:10.1103/physrevb.88.214417

Cited by 141 publications

(160 citation statements)

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“…It is unnecessary to include a Rashba term (p × E SOC ) · σ because p E SOC x in this problem, where E SOC is the effective electric field due to the parity-breaking inx-direction [15][16][17]19]. We consider a FMM much thinner than its spin relaxation length b ≪ l sf such that the wave function …”

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confidence: 99%

“…It is generally suspected that the observed spin torque contains both SHE-STT [13] and the spin-orbit torque (SOT) [15][16][17]19] that stems from the charge current flowing through the parity-breaking FMM. Concerning SOT alone, a field-like component is expected from the current induced spin density [21], yet scattering-related mechanisms [17][18][19][20], as well as intrinsic Berry curvature [22] have been shown to cause a dampinglike torque of similar strength. On the other hand, the mechanism of SHE-STT is less explored, thus the relative weighting between SOT and SHE-STT remains unclear.…”

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Minimal Model of Spin-Transfer Torque and Spin Pumping Caused by the Spin Hall Effect

et al. 2015

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In the normal metal/ferromagnetic insulator bilayer (such as Pt/Y3Fe5O12) and the normal metal/ferromagnetic metal/oxide trilayer (such as Pt/Co/AlOx) where spin injection and ejection are achieved by the spin Hall effect in the normal metal, we propose a minimal model based on quantum tunneling of spins to explain the spin-transfer torque and spin pumping caused by the spin Hall effect. The ratio of their damping-like to field-like component depends on the tunneling wave function that is strongly influenced by generic material properties such as interface s − d coupling, insulating gap, and layer thickness, yet the spin relaxation plays a minor role. The quantified result renders our minimal model an inexpensive tool for searching for appropriate materials. [6,7]. Unlike in metallic heterostructures, the usual way of spin injection by using a spin-polarized charge current in the currentperpendicular-to-plane (CPP) geometry is difficult in NM/FMI because the insulating FMI impedes the charge current. Instead, the spin injection in this system is done by using the spin Hall effect (SHE) in the NM, which in the current-in-plane (CIP) geometry injects a pure spin current into the FMI to cause STT. In the reciprocal process, SHE converts the pure spin current generated from spin pumping into electric signals. Despite pointing at promising applications in magnetic memory devices, the microscopic mechanism concerning how the pure spin current tunnels into an insulator to cause STT and spin pumping remains unclear, especially if spin relaxation plays a crucial role as in metallic heterostructures [1].

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Minimal Model of Spin-Transfer Torque and Spin Pumping Caused by the Spin Hall Effect

et al. 2015

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“…(B20)-(B22) for the case of realistic electronic structures. Such calculations would provide a useful bridge between direct first-principles calculations of spin torques [30,[40][41][42] and drift-diffusion calculations done to analyze experiments.…”

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confidence: 99%

Spin transport at interfaces with spin-orbit coupling: Phenomenology

2016

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This paper presents the boundary conditions needed for drift-diffusion models to treat interfaces with spin-orbit coupling. Using these boundary conditions for heavy metal/ferromagnet bilayers, solutions of the drift-diffusion equations agree with solutions of the spin-dependent Boltzmann equation and allow for a much simpler interpretation of the results. A key feature of these boundary conditions is their ability to capture the role that in-plane electric fields have on the generation of spin currents that flow perpendicularly to the interface. The generation of these spin currents is a direct consequence of the effect of interfacial spin-orbit coupling on interfacial scattering. In heavy metal/ferromagnet bilayers, these spin currents provide an important mechanism for the creation of damping-like and field-like torques; they also lead to possible reinterpretations of experiments in which interfacial contributions to spin torques are thought to be suppressed.

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“…Because of the outstanding advantages and possibly manageable disadvantages mentioned above, the SO-STT switching recently attracts considerable interest from spintronics community, leading to detailed studies about it [32][33][34][35][36][37][38][39]. For the device application, the analytic expression of the switching current…”

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Thermally activated switching of perpendicular magnet by spin-orbit spin torque

Lee

Min

et al. 2014

Applied Physics Letters

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109

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We theoretically investigate the threshold current for thermally activated switching of a perpendicular magnet by spin-orbit spin torque. Based on the Fokker-Planck equation, we obtain an analytic expression of the switching current, in agreement with numerical result. We find that thermal energy barrier exhibits a quasi-linear dependence on the current, resulting in an almost linear dependence of switching current on the log-scaled current pulse-width even below 10 ns. This is in stark contrast to standard spin torque switching, where thermal energy barrier has a quadratic dependence on the current and the switching current rapidly increases at short pulses. Our results will serve as a guideline to design and interpret switching experiments based on spin-orbit spin torque.

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Current-induced torques and interfacial spin-orbit coupling

Cited by 141 publications

References 47 publications

Minimal Model of Spin-Transfer Torque and Spin Pumping Caused by the Spin Hall Effect

Minimal Model of Spin-Transfer Torque and Spin Pumping Caused by the Spin Hall Effect

Spin transport at interfaces with spin-orbit coupling: Phenomenology

Thermally activated switching of perpendicular magnet by spin-orbit spin torque

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