Numerical simulations of critical dynamics in anisotropic magnetic films with the stochastic Landau-Lifshitz-Gilbert equation

Jin, Menghao; Zheng, Bo; Xiong, Lun; Zhou, N. J.; Wang, L.

doi:10.1103/physreve.98.022126

Cited by 11 publications

(9 citation statements)

References 74 publications

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“…Experimental studies verifying these results are needed, and are likely to be challenging due to the need to reach very low temperatures [33,34] (to minimize thermal rounding [2]), and to control the disorder. It would be interesting to extend our study to 3D systems with 2D DWs with internal degrees of freedom [35], to consider effects due to a finite T [36], as well as the interplay of ξ with the DW and BL widths. Our model should find applications in modelling DW dynamics in a wide range of contexts where DW velocities are not so high that spin wave emission from the moving DW [37][38][39] (not captured by our line model) becomes important, including creep motion of DWs [5] and Barkhausen noise [6].…”

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confidence: 99%

Depinning exponents of thin film domain walls depend on disorder strength

Skaugen,

Laurson

2021

Preprint

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Domain wall dynamics in ferromagnets is complicated by internal degrees of freedom of the domain walls. We develop a model of domain walls in disordered thin films with perpendicular magnetic anisotropy capturing such features, and use it to study the depinning transition. For weak disorder, excitations of the internal magnetization are rare, and the depinning transition takes on exponent values of the quenched Edwards-Wilkinson equation. Stronger disorder results in disorder-dependent exponents concurrently with nucleation of an increasing density of Bloch lines within the domain wall.

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confidence: 99%

Depinning exponents of thin film domain walls depend on disorder strength

Skaugen,

Laurson

2021

Preprint

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“…2). Since we use the LLG equation and add stochasticity in the initial angle and the run-time random thermal field, our simulation method is equivalent to the stochastic LLG equation in [43].…”

Section: A Magnetization Dynamicsmentioning

confidence: 99%

Evaluation of Operating Margin and Switching Probability of Voltage- Controlled Magnetic Anisotropy Magnetic Tunnel Junctions

Song

Ahmed

Zhao

et al. 2018

IEEE J. Explor. Solid-State Comput. Devices Circuits

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Voltage-controlled magnetic anisotropy (VCMA) has attracted great attention as it allows faster switching and lower energy consumption compared to traditional spin-transfer torque-based magnetization switching. In this paper, we evaluate the operating margin and switching probability of VCMA-based magnetic tunnel junctions using realistic material and device parameters. For this paper, we developed a physics-based SPICE model that incorporates various VCMA parameters such as VCMA coefficient, energy barrier, time constant, and external magnetic field. Switching probability of a VCMA device was obtained by running Monte Carlo simulations including thermal fluctuation effects. A design space exploration was performed using the proposed simulation framework. The highest switching probabilities we were able to achieve were 94.9%, 84.8%, and 53.5%, for VCMA coefficient values of 33, 105, and 290 fJ • V −1• m −1 , respectively. Our study shows that for VCMA devices to become viable, their switching probability must be improved significantly either through new physics or material innovation.INDEX TERMS Magnetic tunnel junction (MTJ), switching probability, VCMA coefficient, voltage-controlled magnetic anisotropy (VCMA).

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“…Due to critical slowing down, it is very difficult to simulate the stationary state around the depinning phase transition. The nonstationary dynamic approach looks novel and efficient in tackling the dynamic phase transitions, since the measurements are carried out in the short-time regime of the dynamic evolution [35,[44][45][46][47]. In addition, it may avoid the errors induced by the finite time step Δt in the molecular dynamics simulations of the stationary state.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

et al. 2020

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The dynamic pinning effects are significant in manipulating skymions in chiral magnetic materials with quenched disorder. Through numerical simulations of the non-stationary current-driven dynamics of skyrmions with the Landau-Lifshitz-Gilbert equation, the critical current, static and dynamic critical exponents of the depenning phase transition are accurately determined for both adiabatic and non-adiabatic spin-transfer torques and with different strengths of disorder, based on the dynamic scaling behavior far from stationary. We find that the threshold current is insensitive to a small non-adiabatic coefficient of the spin-transfer torque, but dramatically reduced for a large one. The critical exponents indicate that the critical dynamic behavior is robust for different spin-transfer torques in the perpendicular component of the Hall motion, while exhibits a weak universality class in the direction of the driving current. The anisotropic behavior around the depinning phase transition provides a quantitative analysis of the drive-dependent skyrmion Hall effect in experiments. Further, the theoretical analysis using the Thiele's approach is presented, and the critical current and the static exponents support the simulation results.

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Numerical simulations of critical dynamics in anisotropic magnetic films with the stochastic Landau-Lifshitz-Gilbert equation

Cited by 11 publications

References 74 publications

Depinning exponents of thin film domain walls depend on disorder strength

Depinning exponents of thin film domain walls depend on disorder strength

Evaluation of Operating Margin and Switching Probability of Voltage- Controlled Magnetic Anisotropy Magnetic Tunnel Junctions

Anisotropic critical behavior of current-driven skyrmion dynamics in chiral magnets with disorder

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