Magnetization switching through spin-Hall-effect-induced chiral domain wall propagation

Yu, Guoqiang; Upadhyaya, Pramey; Wong, Kin; Jiang, Wanjun; Alzate, Juan G.; Tang, Jianshi; Amiri, Pedram Khalili

doi:10.1103/physrevb.89.104421

Cited by 128 publications

(97 citation statements)

References 30 publications

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“…2b, consistently with previous reports of SOT-induced switching of perpendicularly magnetized layers 1,9,10,[12][13][14]17 . Further, we find that the switching speed increases by increasing the current amplitude, allowing for full magnetization reversal within a sub-ns current pulse (Fig.…”

supporting

confidence: 91%

“…However, these experiments only measured the switching probability as a function of pulse amplitude and duration, while the mechanism and the timescale of magnetization reversal remain unknown. Microscopy studies performed using the magneto-optic Kerr effect have extensively probed SOT-induced DW displacements [14][15][16][17][18][19]28 , revealing the role played by the Dzyaloshinskii-Moriya interaction (DMI) in stabilizing chiral DW structures that have very high mobility 17,18,[29][30][31][32][33] . Such investigations have a spatial resolution of the order of 1 µm, but only probed the static magnetization after current injection, similar to the pulsed switching experiments 1,26,27 .…”

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confidence: 99%

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Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

et al. 2017

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Current-induced spin-orbit torques (SOTs) represent one of the most effective ways to manipulate the magnetization in spintronic devices. The orthogonal torquemagnetization geometry, the strong damping, and the large domain wall velocities inherent to materials with strong spin-orbit coupling make SOTs especially appealing for fast switching applications in nonvolatile memory and logic units. So far, however, the timescale and evolution of the magnetization during the switching process have remained undetected. Here, we report the direct observation of SOTdriven magnetization dynamics in Pt/Co/AlO x dots during current pulse injection.Time-resolved x-ray images with 25 nm spatial and 100 ps temporal resolution reveal that switching is achieved within the duration of a sub-ns current pulse by the fast nucleation of an inverted domain at the edge of the dot and propagation of a tilted domain wall across the dot. The nucleation point is deterministic and alternates between the four dot quadrants depending on the sign of the magnetization, current, and external field. Our measurements reveal how the magnetic symmetry is broken by the concerted action of both damping-like and field-like SOT and show that reproducible switching events can be obtained for over 10 12 reversal cycles. arXiv:1704.06402v1 [cond-mat.mtrl-sci] 21 Apr 2017Controlling the magnetic state of ultrathin heterostructures using electric currents is key to developing nonvolatile memory devices with minimal static and dynamic power consumption 1 . A promising approach for magnetic switching is based on injecting an in-plane current into a ferromagnet/heavy metal bilayer, where the spin-orbit torques (SOTs) 2,3 resulting from the spin Hall effect and interface charge-spin conversion 4-8 provide an efficient mechanism to reverse the magnetization 1,9,10,12-15 and manipulate domain walls (DWs) [16][17][18][19] .SOT switching schemes can be easily integrated into three-terminal magnetic tunnel junctions having either in-plane 10 or out-of-plane 20 magnetization. Although the threeterminal geometry is more demanding in terms of size, it offers desirable features compared to the two-terminal spin-transfer torque (STT) approach presently used in magnetic random access memories (MRAM) 21 . One such feature is the separation of the read and write current paths in the tunnel junction, which avoids electrical stress of the oxide barrier during writing and allows for independent optimization of the tunneling magnetoresistance during reading. The other crucial feature is the switching speed, which is expected to be extremely fast because the spin accumulation inducing the SOTs is orthogonal to the quiescent magnetization, leading to a negligible incubation delay. Such a delay is a major issue for STT devices, since thermal fluctuations result in a switching time distribution that is several ns wide 22,23 . Furthermore, the SOT-induced magnetization dynamics is governed by strong damping in the monodomain regime 24,25 and fast domain wall motion in the m...

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confidence: 99%

Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

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“…It should be noted that the SOT responsible for switching stems from the Pt layer rather than IrMn because of its much higher current density. Assuming that the dampinglike torque is a result of the spin Hall effect solely, we can find the spin Hall angle using θ SHE ¼ ð−2jejM s t F =hÞ × ðΔH L =JÞ, where jej, h, t F , and M s represent the absolute value of the electron's charge, Planck's constant, ferromagnetic layer thickness, and the saturation magnetization of the ferromagnetic layer [31]. Using a superconducting quantum-interference-device measurement, the saturation magnetization is found to be 1100 emu=cm 3 .…”

Section: Current-driven Magnetization Switching With Out-of-planmentioning

confidence: 99%

Joule Heating Effect on Field-Free Magnetization Switching by Spin-Orbit Torque in Exchange-Biased Systems

Lau

et al. 2017

Phys. Rev. Applied

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Switching of magnetization via spin-orbit torque provides an efficient alternative for nonvolatile memory and logic devices. However, to achieve deterministic switching of perpendicular magnetization, an external magnetic field collinear with the current is usually required, which makes these devices inappropriate for practical applications. In this work, we examine the current-induced magnetization switching in a perpendicularly magnetized exchange-biased Pt=CoFe=IrMn system. A magnetic field annealing technique is used to introduce in-plane exchange biases, which are quantitatively characterized. Under proper conditions, field-free current-driven switching is achieved. We study the Joule heating effect, and we show how it can decrease the in-plane exchange bias and degrade the field-free switching. Furthermore, we discuss that the exchange-bias training effect can have similar effects.

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“…Moreover, the contributions of various interfacial effects, such as the Rashba effects, spin Hall effects (SHEs), and Dzyaloshinskii-Moriya interaction (DMI) to the SOT switching also remain elusive. One widely accepted SOT switching mechanism is based on the macrospin model [4], in which the SOT nucleates initial domains through the macrospin model and switches the entire ferromagnet by subsequent domain expansion [4,12,[23][24][25]. In this model, SHEs dominate the SOT switching, which obeys the rule shown in Figs.…”

Section: Introductionmentioning

confidence: 99%

Anomalous spin-orbit torque switching in synthetic antiferromagnets

Almasi

Price

et al. 2017

Phys. Rev. B

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We report that synthetic antiferromagnets (SAFs) can be efficiently switched by spin-orbit torques (SOTs) and the switching scheme does not obey the usual SOT switching rule. We show that both the positive and negative spin Hall angle (SHA)-like switching can be observed in Pt/SAF structures with only positive SHA, depending on the strength of applied in-plane fields. A switching mechanism directly arising from the asymmetric domain expansion is proposed to explain the anomalous switching behaviors. Contrary to the macrospin-based switching model where the SOT switching direction is determined by the sign of SHA, this switching mechanism suggests that the SOT switching direction is dominated by the field-modulated domain wall motion and can be reversed even with the same sign of SHA. The presence of this switching mechanism is further confirmed by the domain wall motion measurements. The anomalous switching behaviors provide important insights for understanding SOT switching mechanisms and also offer novel features for applications.

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Magnetization switching through spin-Hall-effect-induced chiral domain wall propagation

Cited by 128 publications

References 30 publications

Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

Spatially and time-resolved magnetization dynamics driven by spin–orbit torques

Joule Heating Effect on Field-Free Magnetization Switching by Spin-Orbit Torque in Exchange-Biased Systems

Anomalous spin-orbit torque switching in synthetic antiferromagnets

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