Terahertz Antiferromagnetic Spin Hall Nano-Oscillator

Cheng, Ran; Xiao, Di; Brataas, Arne

doi:10.1103/physrevlett.116.207603

Cited by 256 publications

(196 citation statements)

References 46 publications

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“…Therefore, j AF c scales with the antiferromagnetic resonance frequency, which is typically two orders of magnitude larger than the ferromagnetic resonance. As a result, the critical switching current in antiferromagnetic junctions is expected to be two orders of magnitude larger than in ferromagnetic junctions, which is in agreement with the estimation of Cheng et al [42] and still achievable experimentally.…”

Section: Voltage Dependencesupporting

confidence: 89%

Robust spin transfer torque in antiferromagnetic tunnel junctions

2017

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We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque enabling electrical manipulation of the Néel antiferromagnetic order parameter is out of plane, ∼ n × p, while the torque competing with the antiferromagnetic exchange is in plane, ∼ n × (p × n). Here, p and n are the Néel order parameter direction of the reference and free layers, respectively. Their bias dependence shows behavior similar to that in ferromagnetic tunnel junctions, the in-plane torque being mostly linear in bias, while the out-of-plane torque is quadratic. Most importantly, we find that the spin transfer torque in antiferromagnetic tunnel junctions is much more robust against disorder than that in antiferromagnetic metallic spin valves due to the tunneling nature of spin transport.

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Section: Voltage Dependencesupporting

confidence: 89%

Robust spin transfer torque in antiferromagnetic tunnel junctions

2017

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“…Depending on the configuration, the acoustic mode can be excited while the optical mode is damped. Cheng, Xiao, and Brataas (2016) recently demonstrated that spin Hall torque triggers self-sustained THz oscillations, as further discussed in Sec. III.D.…”

Section: Current-driven Dynamicsmentioning

confidence: 81%

“…Current-driven switching and excitations are governed by the same physics. In a recent study, Cheng, Xiao, and Brataas (2016) proposed exploitation of the spin Hall torque to trigger THz oscillations. In their study, they considered the case of a biaxial antiferromagnet and showed that when the spin Hall torque is increased, the frequency of the optical mode is progressively reduced, while the frequency of the acoustic mode is enhanced.…”

Section: B Manipulation By Spin Hall Torquementioning

confidence: 99%

Antiferromagnetic spintronics

et al. 2018

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Antiferromagnetic materials could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics, and are capable of generating large magnetotransport effects. Intense research efforts over the past decade have been invested in unraveling spin transport properties in antiferromagnetic materials. Whether spin transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges currently being addressed. Antiferromagnetic spintronics started out with studies on spin transfer and has undergone a definite revival in the last few years with the publication of pioneering articles on the use of spin-orbit interactions in antiferromagnets. This paradigm shift offers possibilities for radically new concepts for spin manipulation in electronics. Central to these endeavors are the need for predictive models, relevant disruptive materials, and new experimental designs. This paper reviews the most prominent spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials. It also details some of the remaining bottlenecks and suggests possible avenues for future research. This review covers both spin-transfer-related effects, such as spin-transfer torque, spin penetration length, domain-wall motion, and "magnetization" dynamics, and spin-orbit related phenomena, such as (tunnel) anisotropic magnetoresistance, spin Hall, and inverse spin galvanic effects. Effects related to spin caloritronics, such as the spin Seebeck effect, are linked to the transport of magnons in antiferromagnets. The propagation of spin waves and spin superfluids in antiferromagnets is also covered.

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“…Self-oscillations, in the form of limit cycles, are sustained above the critical current j c in the case of the easy-z-axis anisotropy. For the easy-y-axis geometry, the nature of the autonomous dynamics beyond the threshold j c was shown 9 to be sensitive to the details of the Gilbert-damping tensor, which can acquire, in particular, an anisotropic form ∝ l × (l 2 zl +l zêz ). The resultant self-oscillation frequencies belong to the THz range for typical insulating antiferromagnets.…”

Section: 14mentioning

confidence: 99%

“…5,8 It appears particularly attractive to manipulate the staggered order parameter through the spin Hall effect. In the usual antidampingtorque geometry, 9 however, the effective spin accumulation induced by the spin Hall effect must overcome the large gap in the antiferromagnetic spectrum (typically in the range of THz for common materials), translating into prohibitively large charge currents. Therefore, further insights concerning the antiferromagnetic equilibrium states and their spin Hall induced dynamics, in the presence of strong spin-orbit interactions, are desired for further progress.…”

mentioning

confidence: 99%

Antiferromagnetic textures and dynamics on the surface of a heavy metal

Zarzuela

Tserkovnyak

2017

Phys. Rev. B

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We investigate the formation and dynamics of spin textures in antiferromagnetic insulators adjacent to a heavy-metal substrate with strong spin-orbit interactions. Exchange coupling to conduction electrons engenders an effective anisotropy, Dzyaloshinskii-Moriya interactions, and a magnetoelectric effect for the Néel order, which can conspire to produce nontrivial antiferromagnetic textures. Current-driven spin transfer enabled by the heavy metal, furthermore, triggers ultrafast (THz) oscillations of the Néel order for dc currents exceeding a critical threshold, opening up the possibility of Terahertz spin-torque self-oscillators. For a commonly invoked antidamping-torque geometry, however, the instability current scales with the energy gap of the antiferromagnetic insulator and, therefore, may be challenging to reach experimentally. We propose an alternative generic geometry for inducing ultrafast autonomous antiferromagnetic dynamics.Introduction.-Antiferromagnetic spin textures produce minimal stray fields, are robust against electromagnetic perturbations, and display ultrafast spin dynamics, three features that make them attractive as potential active elements in next-generation spin-transport and memory-storage devices.1 Recent years have witnessed a growing interest in the inherently antiferromagnetic (spin) transport properties.2-5 However, the Néel order is relatively hidden from electromagnetic fields and, therefore, generally not easy to drive or read out. In this regard, spin-transfer torques are well suited to trigger antiferromagnetic excitations 6,7 and may be as effective for this purpose as in ferromagnets.5,8 It appears particularly attractive to manipulate the staggered order parameter through the spin Hall effect. In the usual antidampingtorque geometry, 9 however, the effective spin accumulation induced by the spin Hall effect must overcome the large gap in the antiferromagnetic spectrum (typically in the range of THz for common materials), translating into prohibitively large charge currents. Therefore, further insights concerning the antiferromagnetic equilibrium states and their spin Hall induced dynamics, in the presence of strong spin-orbit interactions, are desired for further progress.In this Rapid Communication, we construct a phenomenological theory for antiferromagnetic insulators subjected to spin exchange and spin-orbit coupling with an adjacent heavy metal. We focus on energy terms that favor spin textures, with an eye on nontrivial topologies. Furthermore, we study the Néel order driven out of equilibrium by spin-transfer torques and find the thresholds for current-driven magnetic instabilities for several scenarios, classifying the ensuing nonlinear dynamics. Our primary interest here is in ultrafast self-oscillations of a uniform staggered order, which can be sustained by feasible charge currents (as in, e.g., the ferromagnetic counterparts).Effective theory.-We regard the heterostructure as a quasi-two-dimensional (2D) system along the xy plane, which we take to be isotropic ...

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Terahertz Antiferromagnetic Spin Hall Nano-Oscillator

Cited by 256 publications

References 46 publications

Robust spin transfer torque in antiferromagnetic tunnel junctions

Robust spin transfer torque in antiferromagnetic tunnel junctions

Antiferromagnetic spintronics

Antiferromagnetic textures and dynamics on the surface of a heavy metal

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