Current driven domain wall depinning in notched Permalloy nanowires (original) (raw)
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IOP Conference Series: Materials Science and Engineering
Utilization of topological nanostructure such as magnetic domain wall (DW) as a future generation of non-volatile memory as racetrack memory has been attracted more researchers due to potential to achieve higher speed of data read/writing and capacity. However, completed understanding of DW dynamics was still need to be improved by advanced analysis from the theoretical/simulation or experimental methods. In this study, the effect of geometrical notch dept on domain wall depinning in Permalloy (Py) nanowires by micromagnetic simulation method have been investigated. The varied double notch dept from 10 to 90 nm in 200 nm of wire width were used and the transverse type DW was triggered by nanosecond current pulse to observe the critical depinning current (Jd). It is observed that the depinning current was increased as the notch dept increases. However, the magnitude of Jd have a maximum values for all notch length variation. The increasing of notch length has shifted the maximum Jd to the larger notch dept values. This behavior indicated that the optimum notch design was needed to obtain higher speed and lower depinning energy in the development of domain wall based devices.
Stochastic nature of the domain wall depinning in permalloy magnetic nanowires
Physical Review B, 2010
This study explores experimentally the stochastic nature of the domain wall depinning in permalloy nanowires using notches of various shapes and depths. The presence of the domain wall in the notch is detected through its anisotropic magnetoresistance ͑AMR͒, which is measured with high precision in order to detect even small changes in the domain wall profile. These measurements showed that variations in the depinning field are related with changes, sometimes very small, in the AMR profile, which indicates that small changes in the pinned domain wall profile can affect largely the depinning process. As these small changes are many times unpredictable and uncontrollable, the stochastic nature of the depinning could have negative consequences for practical applications based on permalloy nanowires.
Depinning Field at Notches of Ferromagnetic Nanowires With Perpendicular Magnetic Anisotropy
IEEE Transactions on Magnetics, 2009
In this paper, we experimentally characterize the domain-wall depinning mechanism at notches of ferromagnetic nanowires with perpendicular magnetic anisotropy. A time-resolved magneto-optical Kerr effect detection reveals that the depinning time is exponentially proportional to the strength of external magnetic field. From an analysis based on Néel-Brown theory, the depinning field and the activation volume are quantitatively determined for several notches with different gap distances. Interestingly, both the depinning field and the activation volume are proportional to the inverse of the gap distance. This is explained by the sizeable extrinsic effect from geometric constrictions in contrast to the intrinsic properties of the films.
Journal of the Korean Physical Society, 2013
We have investigated the domain wall (DW) depinning behavior around the symmetric notches in ferromagnetic nanowires by means of a micromagnetic simulation. We observed that the depinning field decreases as the size of the notch increases. The change in the ratio of the height to the length of the bottom of the triangular notch is also considered, and a relatively insensitive variation of the depinning field is observed with for ratios greater than 2. When the depinning field strength is varied, the DW internal structure is found to change during the depinning process. At a lower depinning field (< 4 mT), the DW keeps its initial transverse wall structure whereas at a higher depinning field (> 4 mT), the DW is depinned with a transformation of the inner structure with an antivortex soon after the DW has escaped from the notch due to the Walker breakdown phenomenon. Very interestingly, with any external field, the depinned DW with antivortex inner structure is observed to move back to the original notch position. This is explainable because the notch acts as an attractive pinning potential for the DW.
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.
Energetics of domain wall in magnetic nanowire
Journal of Physics: Conference Series, 2019
Micromagnetic modeling is used to study the energetics of magnetic switching of single-layer permalloy nanowire. The energy landscape of the system is studied using Nudged Elastic Band method. It has been shown that presence of rectangular shape defects on long side and inside nanowire leads to the appearance of local maxima and minima on the energy profile. Thus artificially created imperfections can be used for effective DW pinning.