Current-induced domain-wall switching in a ferromagnetic semiconductor structure

Yamanouchi, Michihiko; Chiba, Daichi; Matsukura, F.; Ohno, Hideo

doi:10.1038/nature02441

Cited by 678 publications

(492 citation statements)

References 26 publications

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“…This value is comparable to the experimentally observed sizes, that is, x ¼ 18 nm for MnSi. The strength of magnetic anisotropy at impurity sites, A/J ¼ 0.2, turns out to give a critical current of j c B10 10 -10 11 A m À 2 for the current-driven motion of the HL texture, which reproduces the experimental value observed for the ferromagnetic domain-wall motion [3][4][5] . The magnetic field B ¼ (0,0,B) is applied normal to the plane where B/J ¼ À 1.5 Â 10 À 2 for the SkX phase, and B ¼ 0 for the HL phase.…”

Section: Resultssupporting

confidence: 67%

“…However, the Joule heating has been a serious issue because a large current density j is necessary to overcome the pinning, and, therefore, the experiments usually have been done using a short pulse of electric current. The current-velocity relation of the domain-wall motion has been well studied [3][4][5][6][7][8][9] , which is sensitive to the impurity pinning, the Gilbert damping, and nonadiabatic effects.…”

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confidence: 99%

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Universal current-velocity relation of skyrmion motion in chiral magnets

2013

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Current-driven motion of the magnetic domain wall in ferromagnets is attracting intense attention because of potential applications such as racetrack memory. There, the critical current density to drive the motion is B10 9 -10 12 A m À 2 . The skyrmions recently discovered in chiral magnets have much smaller critical current density of B10 5 -10 6 A m À 2 , but the microscopic mechanism is not yet explored. Here we present a numerical simulation of Landau-Lifshitz-Gilbert equation, which reveals a remarkably robust and universal currentvelocity relation of the skyrmion motion driven by the spin-transfer-torque unaffected by either impurities or nonadiabatic effect in sharp contrast to the case of domain wall or spin helix. Simulation results are analysed using a theory based on Thiele's equation, and it is concluded that this behaviour is due to the Magnus force and flexible shape-deformation of individual skyrmions and skyrmion crystal, which enable them to avoid pinning centres.

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Section: Resultssupporting

confidence: 67%

mentioning

confidence: 99%

Universal current-velocity relation of skyrmion motion in chiral magnets

2013

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“…Popular approaches include passing a spin current through the soft layer to generate a spin transfer torque [2][3][4][5][6][7] or spin orbit torque [8][9][10][11] or domain wall motion [12][13] . Other approaches involve using voltage controlled magnetic anisotropy 14 , magnetoelectric effects [15][16][17] , magnetoionic effects 18 and magnetoelastic effects [19][20][21][22][23][24][25] .…”

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confidence: 99%

Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

et al. 2017

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Rotating the magnetization of a shape anisotropic magnetostrictive nanomagnet with voltagegenerated stress/strain dissipates much less energy than most other magnetization rotation schemes, but its application to writing bits in non-volatile magnetic memory has been hindered by the fundamental inability of stress/strain to rotate magnetization by full 180 o . Normally, stress/strain can rotate the magnetization of a shape anisotropic elliptical nanomagnet by only up to 90 o , resulting in incomplete magnetization reversal. Recently, we predicted that applying uniaxial stress sequentially along two different axes that are not collinear with the major or minor axis of the elliptical nanomagnet will rotate the magnetization by full 180 o [1]. Here, we demonstrate this complete 180 o rotation in elliptical Co-nanomagnets (fabricated on a piezoelectric substrate) at room temperature. The two stresses are generated by sequentially applying voltages to two pairs of shorted electrodes placed on the substrate such that the line joining the centers of the electrodes in one pair intersects the major axis of a nanomagnet at ~+30 o and the line joining the centers of the electrodes in the other pair intersects at ~ -30 o . A finite element analysis has been performed to determine the stress distribution underneath the nanomagnets when one or both pairs of electrodes are activated, and this has been approximately incorporated into a micromagnetic simulation of magnetization dynamics to confirm that the generated stress can produce the observed magnetization rotations. This result portends an extremely energy-efficient non-volatile "straintronic" memory technology predicated on writing bits in nanomagnets with electrically generated stress.Nanomagnets are the bedrock of non-volatile memory. A magnetic random access memory (MRAM) cell is implemented with a magneto-tunneling junction (MTJ) consisting of two nanomagnetic layers, one hard and one soft, separated by a spacer (tunneling) layer. The soft layer is often shaped like an elliptical disc which, if sufficiently thick, has two in-plane stable magnetization directions pointing in opposite directions along the major axis of the ellipse. They encode and store the binary bits 0 and 1. The stored bit * Corresponding author. E-mail: sbandy@vcu.edu is "read" by measuring the resistance of the MTJ which has two discrete values depending on the two magnetization orientations of the soft layer, i.e., for the two bits 0 and 1. "Writing" of bits is accomplished by switching the magnetization of the soft layer between the two anti-parallel directions of stable magnetization (180 0 rotation of the magnetization) with an external agent.There are many strategies to rotate the magnetization of the soft layer. Popular approaches include passing a spin current through the soft layer to generate a spin transfer torque 2-7 or spin orbit torque [8][9][10][11] or domain wall motion [12][13] . Other approaches involve using voltage controlled magnetic anisotropy 14 , magnetoelectric effects 15-17 ...

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“…CIDWM was also observed in a magnetic semiconductor at a low temperature, for which a much lower threshold current density was realized. [18][19][20] However, the slow DW velocity as well as the low-temperature characteristics of magnetic semiconductors prevented its direct application. For this reason, much attention was devoted to metallic systems such as Py.…”

Section: Progress In Study Of Current-induced Domain Wall Motionmentioning

confidence: 99%

Current-driven magnetic domain wall motion and its real-time detection

Kim

Yoshimura

Ono

2017

Jpn. J. Appl. Phys.

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Current-controlled magnetic domain wall motion has opened the possibility of a novel type of shift register memory device, which has been optimistically predicted to replace existing magnetic memories. Owing to this promising prospect, intensive work has been carried out during the last few decades. In this article, we first review the progress in the study of current-induced magnetic domain wall motion. Underlying mechanisms behind the domain wall motion, which have been discovered during last few decades, as well as technological achievements are presented. We then present our recent experimental results on the real-time detection of current-driven multiple magnetic domain wall motion, which directly demonstrates the operation of a magnetic domain wall shift register.

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Current-induced domain-wall switching in a ferromagnetic semiconductor structure

Cited by 678 publications

References 26 publications

Universal current-velocity relation of skyrmion motion in chiral magnets

Universal current-velocity relation of skyrmion motion in chiral magnets

Experimental Demonstration of Complete 180° Reversal of Magnetization in Isolated Co Nanomagnets on a PMN–PT Substrate with Voltage Generated Strain

Current-driven magnetic domain wall motion and its real-time detection

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