Thermally stable magnetic skyrmions in multilayer synthetic antiferromagnetic racetracks

Zhang, Xichao; Ezawa, Motohiko; Zhou, Yan

doi:10.1103/physrevb.94.064406

Cited by 88 publications

(65 citation statements)

References 69 publications

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“…The size of skyrmions which is dependent on K u results in minor expansion of the skyrmions when they are subjected to an increasing K u gradient. Results presented in figure 3 verifies the linear relationship between skyrmion speed and K u gradient shown in equation (8). Figure 3 also shows a decrease in speed with increasing K u value at the centre of the skyrmion.…”

Section: Skyrmion Velocity Dependence On Magnetic Anisotropy Strengthsupporting

confidence: 73%

“…Magnetic skyrmions are particle-like chiral magnetization states that are promising as an information carrier due to their attractive characteristics such as nanometre dimensions, and topological stability [1][2][3][4][5][6][7][8][9][10][11]. In the implementation of a magnetic skyrmion racetrack memory, the transport techniques explored thus far have been mainly limited to the use of spin-polarized electrical current injection which utilizes spin transfer torque (STT) and spin-orbit torque (SOT).…”

Section: Introductionmentioning

confidence: 99%

“…In our work, we derive an analytical model for the dynamics of VCMA gradient-driven skyrmion pair in synthetic antiferromagnetic bilayer structure. The synthetic antiferromagnetic bilayer structure aims to surpass the velocity limit of the monolayer structure due to the skyrmion Hall effect [8,[38][39][40]. A restoring force that is almost ten times greater than the original driving arising from the interlayer exchange coupling raises the maximum possible velocity of skyrmions to the order of km/s.…”

Section: Introductionmentioning

confidence: 99%

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Bilayer skyrmion dynamics on a magnetic anisotropy gradient

2019

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Magnetic skyrmion transport has been primarily based on the use of spin torques which require high current densities and face performance deterioration associated with Joule heating. In this work, we derive an analytical model for energy efficient skyrmion propagation in an antiferromagneticallycoupled bilayer structure using a magnetic anisotropy gradient. The interlayer skyrmion coupling provides a strong restoring force between the skyrmions, which not only prevents annihilation but also increases their forward velocity up to the order of km s -1 . For materials with low Gilbert damping parameter, the interlayer skyrmion coupling force can be amplified up to ten times, with a corresponding increase in velocity. Furthermore, the analytical model also provides insights into the dynamics of skyrmion pinning and relaxation of asymmetric skyrmion pairs in bilayer-coupled skyrmion systems.

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Section: Skyrmion Velocity Dependence On Magnetic Anisotropy Strengthsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bilayer skyrmion dynamics on a magnetic anisotropy gradient

2019

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“…The nanotrack was simulated with a cell size of 1 nm 3 , in the dimension of 500 nm x 50 nm x 1 nm. The magnetic parameters taken from previous studies were as follows: exchange stiffness A ex = 15 × 10 −12 J m −1 , the damping parameter α = 0.3, saturation magnetization M s = 5.8 × 10 5 A m −1 , perpendicular anisotropy constant K u = 8 × 10 5 J m −3 , and spin Hall angle θ SH = 0.40. The value of DMI constant D for nanotrack was set to 3.0 × 10 −3 J m −2 , and for the DMI energy wells, D was varied from 0.0 to 3.0 × 10 −3 J m −2 .…”

mentioning

confidence: 99%

Effect of Dzyaloshinskii–Moriya Interaction Energy Confinement on Current‐Driven Dynamics of Skyrmions

Bhatti

Piramanayagam

2019

Physica Rapid Research Ltrs

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Magnetic skyrmions, which are topological spin configuration, have gained interest in the past few years. However, skyrmions suffer from the skyrmion Hall effect, a phenomenon where skyrmions deflect from the path of the electron flow and annihilate at the edge of the track. There are attempts to overcome this effect using synthetic antiferromagnetic layer structures and ferrimagnetic layer structures. Herein, a new approach based on introducing Dzyaloshinskii–Moriya interaction (DMI) energy wells is reported to direct the motion of skyrmions in a nanowire. It is shown through simulations that by creating DMI energy wells with a critical DMI value, a skyrmion moves within the boundaries set by the energy wells. It is also shown that the diameter of a skyrmion can be reduced by decreasing the space between the DMI energy wells. The proposed DMI energy well enables packing of skyrmion tracks at a high density. In this view, the effect of magnetostatic interactions between multiple skyrmions on their motion in parallel tracks is also investigated. Furthermore, the effect of changing the distance between skyrmions on magnetostatic interactions is studied. These results offer a new path toward maneuvering the skyrmion motion for racetrack memory or logic devices.

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“…The magnetic parameters used in our micromagnetic simulations are adopted from refs. as follows: saturation magnetization M s = 5.8 × 10 5 A m −1 ; exchange stiffness A ex = 15 × 10 −12 J m −1 ; the DMI constant D = 3 × 10 −3 J m −2 ; the damping parameter α = 0.3; the spin Hall angle θ SH = 0.04, and the perpendicular anisotropy constant K u = 7 × 10 5 J m −3 . We have used MuMax3 for simulations, which provides induced DMI for thin films with out‐of‐plane symmetry breaking, yielding an effective field term which is included in the effective field.…”

mentioning

confidence: 99%

High Amplitude Microwave Generation Using Domain Wall Motion in a Nanowire

Bhatti

Piramanayagam

2018

Physica Rapid Research Ltrs

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Microwave generation has been extensively investigated due to their application in telecommunication and promising use in emerging technologies like internet‐of‐things (IoT) devices. The current approaches to generate microwave using voltage‐controlled oscillators have the problem of high power consumption. Spin torque oscillators have been investigated as an alternative, but they suffer from a weak output signal. Hence, there is a need for an alternative approach which overcomes these issues. Here a new approach is reported, which relies on the motion of domain walls to generate microwave with strong signal and lower power consumption. In this study, a magnetic nanowire with a sequence of oppositely magnetized domains in one half of the nanowire is simulated. The domain walls are moved by applying spin–orbit torque to the nanowire. It is proposed to generate microwave by detecting the changes in magnetization value using a magnetic tunnel junction in real application. The oscillating frequency of magnetization is found to be in GHz. It is demonstrated that the frequency can be tuned by varying the applied current density. The outcome of this work promises the application of the reported method to generate microwave in nanoscale devices of the future.

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Thermally stable magnetic skyrmions in multilayer synthetic antiferromagnetic racetracks

Cited by 88 publications

References 69 publications

Bilayer skyrmion dynamics on a magnetic anisotropy gradient

Bilayer skyrmion dynamics on a magnetic anisotropy gradient

Effect of Dzyaloshinskii–Moriya Interaction Energy Confinement on Current‐Driven Dynamics of Skyrmions

High Amplitude Microwave Generation Using Domain Wall Motion in a Nanowire

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