Spin torque control of antiferromagnetic moments in NiO

Moriyama, Takahiro; Oda, Kazuhiro; Ohkochi, Takuo; Kimata, Motoi; Ono, Teruo

doi:10.1038/s41598-018-32508-w

Cited by 221 publications

(195 citation statements)

References 29 publications

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“…If we focus on the initial and final states alone, the deterministic switching of the octupole polarization T in Mn3Sn is overall analogous to that of the magnetization in FMs because the same symmetry requirements apply to both cases. However, we note that the emergence of the same steady states irrespective of the sign of Iwrite ( In recent years, AFMs have attracted significant attention as they have vanishingly small stray fields perturbing neighboring cells and much faster spin dynamics than ferromagnetic counterparts [24][25][26] , leading to the breakthrough of the electrical-current control of AF sublattices and its detection using anisotropic or spin Hall magnetoresistance [54][55][56][57][58][59] . However, contrary to conventional FM spintronics, these emerging technologies require additional operation 11 schemes to apply current along different directions from the crystalline axes, hampering their integration to conventional spintronics.…”

mentioning

confidence: 94%

Electrical manipulation of a topological antiferromagnetic state

Tsai

Higo

Kondou

et al. 2020

Nature

248

212

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† These authors contributed equally to this work. Electrical manipulation of emergent phenomena due to nontrivial band topology is a key to realize next-generation technology using topological protection. A Weyl semimetal is a three-dimensional gapless system that hosts Weyl fermions as low-energy quasiparticles 1-4 . It exhibits various exotic phenomena such as large anomalous Hall effect (AHE) and chiral anomaly, which have robust properties due to the topologically protected Weyl nodes 1-23 . To manipulate such phenomena, the magnetic version of Weyl semimetals would be useful as a magnetic texture may provide a handle for controlling the locations of Weyl nodes in the Brillouin zone. Moreover, given the prospects of antiferromagnetic (AF) spintronics for realizing high-density devices with ultrafast operation 24-26 , it would 2 be ideal if one could electrically manipulate an AF Weyl metal. However, no report has appeared on the electrical manipulation of a Weyl metal. Here we demonstrate the electrical switching of a topological AF state and its detection by AHE at room temperature. In particular, we employ a polycrystalline thin film 27 of the AF Weyl metal Mn3Sn 10,13,15,28 , which exhibits zero-field AHE. Using the bilayer device of Mn3Sn and nonmagnetic metals (NMs), we find that an electrical current density of ~10 10 -10 11 A/m 2 in NMs induces the magnetic switching with a large change in Hall voltage, and besides, the current polarity along a bias field and the sign of the spin Hall angle θSH of NMs [Pt (θSH > 0) 29 , Cu(θSH ~ 0), W (θSH < 0) 30 ] determines the sign of the Hall voltage. Notably, the electrical switching in the antiferromagnet is made using the same protocol as the one used for ferromagnetic metals 31,32 . Our observation may well lead to another leap in science and technology for topological magnetism and AF spintronics 33 . Recent extensive studies in condensed matter physics have led to the discoveries of novel quantum phases with nontrivial topology in the electronic band structure 4,34,35 . One example of such topological systems is a Weyl semimetal 1-4 . Two non-degenerate bands linearly touch at a pair of momentum points, forming gapless Weyl fermions with different chiralities in a timereversal-symmetry (TRS) or inversion-symmetry breaking state. These touching points or Weyl nodes act as topologically protected, unit-strength (anti)monopoles of underlying Berry curvature, and lead to various emergent phenomena such as large AHE, anomalous Nernst effect (ANE), chiral anomaly and optical gyrotropy 1-23 .For developing science and technology utilizing novel topological states, a crucial next step would be to manipulate these emergent phenomena electrically. In a Weyl semimetal, the manipulation can be made by moving the Weyl points around in the Brillouin zone. For this purpose, the TRS breaking or magnetic Weyl semimetals are suitable as their magnetic texture 3 may provide a handle for the manipulation. Besides, antiferromagnets (AFMs) have recently attracted significant atte...

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confidence: 94%

Electrical manipulation of a topological antiferromagnetic state

Tsai

Higo

Kondou

et al. 2020

Nature

248

212

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“…The prototype memory devices based on Pt/NiO bilayer structures were recently demonstrated independently by two groups, the results of which are shown in Fig. 4g, h 36,37 .…”

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confidence: 97%

Spin transport in antiferromagnetic insulators: progress and challenges

2019

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Spin transport is a key process in the operation of spin-based devices that has been the focus of spintronics research for the last two decades. Conductive materials, such as semiconductors and metals, in which the spin transport relies on electron diffusion, have been employed as the channels for spin transport in most studies. Due to the absence of conduction electrons, the potential to be a spin channel has long been neglected for insulators. However, since the demonstration of spin transmission through a ferromagnetic insulator, it was realized that insulators with magnetic ordering can also serve as channels for spin transport. Here, the recent progress of spin transport in antiferromagnetic insulators is briefly described with an introduction to the experimental techniques. The observations regarding the temperature dependence of spin transmission, spin current switching and the negative spin Hall magnetoresistance are discussed. We also include the challenges for developing the functionality of antiferromagnetic insulators as well as the unresolved problems from the experimental observations.

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“…This means that metallic AFM materials, like M n 2 Au or IrMn could be more suitable for the practical design of the AFM-based spike generators, than the dielectric AFM , like NiO. The use of conductive AFM layers in a spike generator can also substantially enhance the magnitude of the output signal by employing the "AFM tunneling magnetoresistance effect" [23,24] instead of the ISHE in the adjacent Pt layer to extract the output spike signal from the AFM material.…”

Section: Figmentioning

confidence: 99%

Ultra-fast artificial neuron: generation of picosecond-duration spikes in a current-driven antiferromagnetic auto-oscillator

Khymyn

Lisenkov

Voorheis

et al. 2018

Sci Rep

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We demonstrate analytically and numerically, that a thin film of an antiferromagnetic (AFM) material, having biaxial magnetic anisotropy and being driven by an external spin-transfer torque signal, can be used for the generation of ultra-short “Dirac-delta-like” spikes. The duration of the generated spikes is several picoseconds for typical AFM materials and is determined by the inplane magnetic anisotropy and the effective damping of the AFM material. The generated output signal can consist of a single spike or a discrete group of spikes (“bursting”), which depends on the repetition (clock) rate, amplitude, and shape of the external control signal. The spike generation occurs only when the amplitude of the control signal exceeds a certain threshold, similar to the action of a biological neuron in response to an external stimulus. The “threshold” behavior of the proposed AFM spike generator makes possible its application not only in the traditional microwave signal processing but also in the future neuromorphic signal processing circuits working at clock frequencies of tens of gigahertz.

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Spin torque control of antiferromagnetic moments in NiO

Cited by 221 publications

References 29 publications

Electrical manipulation of a topological antiferromagnetic state

Electrical manipulation of a topological antiferromagnetic state

Spin transport in antiferromagnetic insulators: progress and challenges

Ultra-fast artificial neuron: generation of picosecond-duration spikes in a current-driven antiferromagnetic auto-oscillator

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