Dynamical Pinning of a Domain Wall in a Magnetic Nanowire Induced by Walker Breakdown

Tanigawa, H.; Koyama, Tanetoshi; Bartkowiak, Maciej; Kasai, S.; Kobayashi, Kensuke; Ono, Teruo; Nakatani, Yoshinobu

doi:10.1103/physrevlett.101.207203

Cited by 37 publications

(38 citation statements)

References 33 publications

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“…When the driving fi eld is between the Walker breakdown fi eld (15 Oe) and the static propagation fi eld (25 Oe), both the wall ' s velocity and its propagation distance are widely distributed, in good agreement with experiments. We note that the concept of dynamic DW pinning has previously been inferred by studying the transmission probability of vortex DWs between two positions in a nanowire 10 or by measuring the diff erent depinning fi elds of static and kinetic DWs at a notch 17 . Our experiments, in contrast, provide direct evidence that the DW is not necessarily pinned at the strongest pinning sites along the wire, as identifi ed in small or zero fi elds, but rather the phase of the DW ' s oscillatory precession along the nanowire has a key role.…”

Section: Discussionmentioning

confidence: 99%

Enhanced stochasticity of domain wall motion in magnetic racetracks due to dynamic pinning

et al. 2010

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Understanding the details of domain wall (DW) motion along magnetic racetracks has drawn considerable interest in the past few years for their applications in non-volatile memory devices. The propagation of the DW is dictated by the interplay between its driving force, either fi eld or current, and the complex energy landscape of the racetrack. In this study, we use spin-valve nanowires to study fi eld-driven DW motion in real time. By varying the strength of the driving magnetic fi eld, the propagation mode of the DW can be changed from a simple translational mode to a more complex precessional mode. Interestingly, the DW motion becomes much more stochastic at the onset of this propagation mode. We show that this unexpected result is a consequence of an unsustainable gain in Zeeman energy of the DW, as it is driven faster by the magnetic fi eld. As a result, the DW periodically releases energy and thereby becomes more susceptible to pinning by local imperfections in the racetrack.

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Section: Discussionmentioning

confidence: 99%

Enhanced stochasticity of domain wall motion in magnetic racetracks due to dynamic pinning

et al. 2010

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“…The existence of distinct static and kinetic depinning fields for viscous DW motion ͑below the Walker field͒ has been demonstrated in simulations 6 and investigated experimentally. 7 Kinetic depinning has also been observed indirectly as a "dynamical pinning" effect, 8,9 which occurs when the Walker field lies in between the static and kinetic pinning fields of a random potential due to edge roughness. In this paper we study the situation where the DW motion takes place above the Walker field and the DW interacts with a single, welldefined pinning site.…”

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confidence: 99%

Kinetic depinning of a magnetic domain wall above the Walker field

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et al. 2011

Applied Physics Letters

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Domain wall propagation in micrometric wires: Limits of single domain wall regime J. Appl. Phys. 111, 07E311 (2012) Magnetic structure and resonance properties of a hexagonal lattice of antidots Low Temp. Phys. 38, 157 (2012) Thermally activated domain wall dynamics in a disordered magnetic nanostrip J. Appl. Phys. 109, 07D345 (2011) Noise investigation of the orthogonal fluxgate employing alternating direct current bias J. Appl. Phys. 109, 07E529 (2011) Comparison of electrical techniques for magnetization dynamics measurements in micro/nanoscale structures

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“…Dynamical pinning effects have also been observed in experiments of field-driven vortex wall dynamics. 13,14 However, despite these advances, many details of the disorder effects on DW dynamics in nanostructures remain to be clarified.In this paper, we consider by micromagnetic simulations the effect of disorder on the field and current-driven dynamics of a transverse DW in a narrow and thin permalloy strip. Disorder is modeled by including randomly positioned small nonmagnetic regions (voids) in the system.…”

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Effect of disorder on transverse domain wall dynamics in magnetic nanostrips

2012

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We study the effect of disorder on the dynamics of a transverse domain wall in ferromagnetic nanostrips, driven either by magnetic fields or spin-polarized currents, by performing a large ensemble of graphics processing unit-accelerated micromagnetic simulations. Disorder is modeled by including small, randomly distributed nonmagnetic voids in the system. Studying the domain wall velocity as a function of the applied field and current density reveals fundamental differences in the domain wall dynamics induced by these two modes of driving: For the field-driven case, we identify two different domain wall pinning mechanisms, operating below and above the Walker breakdown, respectively, whereas for the current-driven case pinning is absent above the Walker breakdown. Increasing the disorder strength induces a larger Walker breakdown field and current, and leads to decreased and increased domain wall velocities at the breakdown field and current, respectively. Furthermore, for adiabatic spin-transfer torque, the intrinsic pinning mechanism is found to be suppressed by disorder. We explain these findings within the one-dimensional model in terms of an effective damping parameter α * increasing with the disorder strength. Domain wall (DW) dynamics in nanoscale ferromagnetic wires and strips driven by magnetic fields or spin-polarized currents is a subject of major technological importance for the operation of potential future nanoscale magnetic memory 1,2 and logic 3 devices. In these devices information is typically stored as magnetic domains along a nanostrip or wire and is processed by DW motion. For the reliable operation of such devices it is of fundamental importance to understand and control the effect of imperfections or disorder on the DW dynamics, necessarily present in any realistic samples, e.g., in the form of thickness fluctuations and grain structure of the sample, or various impurities and defects in the material. At the same time, such systems constitute a low-dimensional limit of the general problem of driven elastic manifolds in a random potential. 4 While the crucial importance of disorder for the dynamics of higher-dimensional DWs is well established, resulting in phenomena such as the Barkhausen effect, 5 a majority of studies of DW motion in systems with nanostrip or wire geometry neglect disorder effects. This applies to both theoretical studies and interpretations of experimental results. Some exceptions include studies demonstrating enhanced DW propagation due to the roughness of the edges of the strip. 6,7 Recently also the effect of spatially varying saturation magnetization M s on the dynamics of vortex walls was studied, resulting in an effective damping increasing with the disorder strength.8 Similar spatially distributed disorder has also been studied in a simplified, line-based model of a transverse DW.9,10 Experimental studies of DW dynamics in wires have revealed its stochastic nature in the case of short current pulses, 11 and has been attributed to the presence of disorder in...

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Dynamical Pinning of a Domain Wall in a Magnetic Nanowire Induced by Walker Breakdown

Cited by 37 publications

References 33 publications

Enhanced stochasticity of domain wall motion in magnetic racetracks due to dynamic pinning

Enhanced stochasticity of domain wall motion in magnetic racetracks due to dynamic pinning

Kinetic depinning of a magnetic domain wall above the Walker field

Effect of disorder on transverse domain wall dynamics in magnetic nanostrips

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