OOMMF user's guide, version 1.0

Donahue, Michael J.; Porter, Donald G.

doi:10.6028/nist.ir.6376

Cited by 1,722 publications

(1,250 citation statements)

References 2 publications

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“…Further thickness increases are accompanied by receding remanence and coercivity. While our semiquantitative micromagnetic (Oommf) 14 simulations of a single tube isolated in vacuum allow one to expect the initial increase in H c // with d w , they do not reproduce the trend observed for 13 nm < d w < 20 nm ( Figure S7). Consequently, we ascribe the latter to the interaction of each tube with the stray fields produced by the arraysan effective antiferromagnetic coupling between neighboring tubes, which reduces H c // as previously demonstrated for the case of nickel nanowires.…”

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confidence: 68%

Ordered Iron Oxide Nanotube Arrays of Controlled Geometry and Tunable Magnetism by Atomic Layer Deposition

et al. 2007

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Iron oxide nanotubes of 50−150 nm outer diameter and 2−20 nm wall thickness are prepared in ordered arrays. Atomic layer deposition (ALD) of Fe2O3 from the precursor iron(III) tert-butoxide at 130−180 °C yields very smooth coverage of the pore walls of anodic alumina templates, with thickness growth of 0.26(±0.04) Å per cycle. The reduced Fe3O4 tubes are hard ferromagnets, and variations of the wall thickness d w have marked consequences on the magnetic response of the tube arrays. For 50 nm outer diameter, tubes of d w = 13 nm yield the largest coercive field (H c > 750 Oe), whereas lower coercivities are observed on both the thinner and thicker sides of this optimum.

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confidence: 68%

Ordered Iron Oxide Nanotube Arrays of Controlled Geometry and Tunable Magnetism by Atomic Layer Deposition

et al. 2007

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“…Full micromagnetic simulations based on the extended LLG equations incorporating both adiabatic and non-adiabatic spin torque effects were conducted 27 and compared with the analytical models at selected frequencies to verify that the model provides an accurate description of the vortex dynamics for our sample parameters. Simulations of a square, 2,000×2,000×50 nm 3 , represented using cells of 4×4 nm, were conducted using materials parameters for permalloy: saturation magnetization M s = 8.00×10 5 (c) Vortex core precession orbit amplitude versus driving frequency extracted from Lorentz micrographs.…”

Section: Methodsmentioning

confidence: 99%

Direct dynamic imaging of non-adiabatic spin torque effects

et al. 2012

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spin-transfer torques offer great promise for the development of spin-based devices. The effects of spin-transfer torques are typically analysed in terms of adiabatic and non-adiabatic contributions. Currently, a comprehensive interpretation of the non-adiabatic term remains elusive, with suggestions that it may arise from universal effects related to dissipation processes in spin dynamics, while other studies indicate a strong influence from the symmetry of magnetization gradients. Here we show that enhanced magnetic imaging under dynamic excitation can be used to differentiate between non-adiabatic spin-torque and extraneous influences. We combine Lorentz microscopy with gigahertz excitations to map the orbit of a magnetic vortex core with < 5 nm resolution. Imaging of the gyrotropic motion reveals subtle changes in the ellipticity, amplitude and tilt of the orbit as the vortex is driven through resonance, providing a robust method to determine the non-adiabatic spin torque parameter β = 0.15 ± 0.02 with unprecedented precision, independent of external effects.

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“…The experimental results were also compared with simulations using the OOMMF code. 25 Material parameters suitable for polycrystalline Co were used (saturation magnetization M S =1.4×10 6 A/m, exchange stiffness A=1.3×10 -11 J/m, and crystalline anisotropy was neglected).…”

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confidence: 99%

Chirality control via double vortices in asymmetric Co dots

et al. 2011

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Reproducible control of the magnetic vortex state in nanomagnets is of critical importance. We report on chirality control by manipulating the size and/or thickness of asymmetric Co dots. Below a critical diameter and/or thickness, chirality control is achieved by the nucleation of single vortex. Interestingly, above these critical dimensions chirality control is realized by the nucleation and subsequent coalescence of two vortices, resulting in a single vortex with the opposite chirality as found in smaller dots. Micromagnetic simulations and magnetic force microscopy highlight the role of edge-bound halfvortices in facilitating the coalescence process.Comment: 15 pages, 4 figure

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OOMMF user's guide, version 1.0

Cited by 1,722 publications

References 2 publications

Ordered Iron Oxide Nanotube Arrays of Controlled Geometry and Tunable Magnetism by Atomic Layer Deposition

Ordered Iron Oxide Nanotube Arrays of Controlled Geometry and Tunable Magnetism by Atomic Layer Deposition

Direct dynamic imaging of non-adiabatic spin torque effects

Chirality control via double vortices in asymmetric Co dots

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