Tuning domain wall dynamics by shaping nanowires cross-sections (original) (raw)
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Fast magnetic domain-wall motion in a ring-shaped nanowire driven by a voltage
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Magnetic domain-wall motion driven by a voltage dissipates much less heat than by a current, but none of the existing reports have achieved speeds exceeding 100 m/s. Here phase-field and finite-element simulations were combined to study the dynamics of strain-mediated voltage-driven magnetic domain-wall motion in curved nanowires. Using a ring-shaped, rough-edged magnetic nanowire on top of a piezoelectric disk, we demonstrate a fast voltage-driven magnetic domain-wall motion with average velocity up to 550 m/s, which is comparable to current-driven wall velocity. An analytical theory is derived to describe the strain dependence of average magnetic domain-wall velocity. Moreover, one 180° domain-wall cycle around the ring dissipates an ultrasmall amount of heat, as small as 0.2 fJ, approximately 3 orders of magnitude smaller than those in current-driven cases. These findings suggest a new route toward developing high-speed, low-power-dissipation domain-wall spintronics.
Coupled domain wall oscillations in magnetic cylindrical nanowires
Journal of Applied Physics, 2015
We report on transverse domain wall (DW) dynamics in two closely spaced cylindrical nanowires. The magnetostatically coupled DWs are shown to undergo an intrinsic oscillatory motion along the nanowire length in addition to their default rotational motion. In the absence of external forces, the amplitude of the DW oscillation is governed by the change in the frequency of the DW rotation. It is possible to sustain the DW oscillations by applying spin-polarized current to the nanowires to balance the repulsive magnetostatic coupling. The current density required to sustain the DW oscillation is found to be in the order of 10 5 A/cm 2. Morover, our analysis of the oscillation reveals that the DWs in cylindrical nanowires possess a finite mass. V
Current-driven domain-wall dynamics in curved ferromagnetic nanowires
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The current-induced motion of a domain wall in a semicircle nanowire with applied Zeeman field is investigated. Starting from a micromagnetic model we derive an analytical solution which characterizes the domain-wall motion as a harmonic oscillation. This solution relates the micromagnetic material parameters with the dynamical characteristics of a harmonic oscillator, i.e., domain-wall mass, resonance frequency, damping constant, and force acting on the wall. For wires with strong curvature the dipole moment of the wall as well as its geometry influence the eigenmodes of the oscillator. Based on these results we suggest experiments for the determination of material parameters which otherwise are difficult to access. Numerical calculations confirm our analytical solution and show its limitations.
Current-induced motion of a domain wall in a magnetic nanowire
Physical Review B, 2006
The current-induced motion of a magnetic domain wall in a quasi-one-dimensional ferromagnet with both easy-axis and easy-plane anisotropies is studied theoretically. We analyze the spin-transfer-induced torque on a sharp domain wall upon the flow of a dc electric current in the wire. The torque is shown to have two components; one of them acts as a driving force on the domain wall. The other torque component leads to changes to the domain-wall shape in that it forces the magnetic moments to diverge from the easy plane.
Enhanced spin transfer torque effect for transverse domain walls in cylindrical nanowires
Physical Review B, 2011
Recent studies have predicted extraordinary properties for transverse domain walls in cylindrical nanowires: zero depinning current, the absence of the Walker breakdown, and applications as domain wall oscillators. In order to reliably control the domain wall motion, it is important to understand how they interact with energy barriers, which may be engineered for example through modulations in the nanowire geometry (such as notches or extrusions) or as inhomogeneities in the material's crystal anisotropy.
IEEE Transactions on Magnetics, 2010
We have investigated a damped oscillatory behavior of domain wall propagation in wavy nanowires under an external field higher than the Walker breakdown field using micromagnetic simulation. In nanowires having sinusoidal edge distortions with variation of wavelengths, domain wall has been observed to pseudomorphically follow the sinusoidal wires with keeping an intrinsic transformational frequency of inner wall spin structure. Oscillation amplitude of the domain wall position decreases as the wavelength of the wire decreases by an interaction between the periodically distributed spins and the propagating domain wall. Oscillatory behavior of the domain wall position is found to decay in a wire having the wavelength well matching with an intrinsic transformational frequency of the propagating domain wall.
Domain-Wall Dynamics in Translationally Nonivariant Nanowires: Theory and Applications
Physical Review Letters, 2012
We generalize domain-wall dynamics to the case of translationally non-invariant ferromagnetic nanowires. The obtained equations of motion make the description of the domain-wall propagation more realistic by accounting for the variations along the wire, such as disorder or change in the wire shape. We show that the effective equations of motion are very general and do not depend on the model details. As an example of their use, we consider an hourglass-shaped nanostrip in detail. A transverse domain wall is trapped in the middle and has two stable magnetization directions. We study the switching between the two directions by short current pulses. We obtain the exact time dependence of the current pulses required to switch the magnetization with the minimal Ohmic losses per switching. Furthermore, we find how the Ohmic losses per switching depend on the switching time for the optimal current pulse. As a result, we show that as a magnetic memory this nanodevice can be 10 5 times more energy efficient than the best modern devices.
Domain wall dynamics in nanowires
Journal of Magnetism and Magnetic Materials, 2002
We study, by numerical calculations, the static domain wall structures in nanowires with axial magnetization. Then, applying an axial field, the wall dynamics is computed and compared to analytical models. We show that the onedimensional Bloch wall dynamics, as first described by Walker, is fully realized in such samples. r
Domain-wall dynamics in translationally non-invariant nanowires: theory and applications
Arxiv preprint arXiv:1109.2996, 2011
We generalize domain-wall dynamics to the case of translationally non-invariant ferromagnetic nanowires. The obtained equations of motion make the description of the domain-wall propagation more realistic by accounting for the variations along the wire, such as disorder or change in the wire shape. We show that the effective equations of motion are very general and do not depend on the model details. As an example of their use, we consider an hourglass-shaped nanostrip in detail. A transverse domain wall is trapped in the middle and has two stable magnetization directions. We study the switching between the two directions by short current pulses. We obtain the exact time dependence of the current pulses required to switch the magnetization with the minimal Ohmic losses per switching. Furthermore, we find how the Ohmic losses per switching depend on the switching time for the optimal current pulse. As a result, we show that as a magnetic memory this nanodevice may be 10 5 times more energy efficient than the best modern devices.