Surface Roughness Dominated Pinning Mechanism of Magnetic Vortices in Soft Ferromagnetic Films

Chen, Te‐Yu; Erickson, M. J.; Crowell, P. A.; Leighton, Chris

doi:10.1103/physrevlett.109.097202

Cited by 49 publications

(56 citation statements)

References 22 publications

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“…Micromagnetic simulations predict significant contribution of higher order energy terms 16,17 leading to a nonlinear increase of the eigenfrequency as a function of the vortex core position. However, the experimental results obtained from eigenfrequency measurements at high-amplitude rf-field excitations or low amplitude rffield excitations in a biasing field are often inconsistent with the simulations, showing a decrease of the eigenfrequency with an increasing amplitude 19 or a pinning dominated dependence on the eigenfrequency 20,21 . Only recently, an experimental measurement of anharmonicity of a potential well in a FeV single crystal disk showed a ∼10% increase of the eigenfrequency for vortex core displacements up to 0.4R, where R is the radius of the disk 18 .…”

Section: Introductionmentioning

confidence: 89%

Dynamics and efficiency of magnetic vortex circulation reversal

et al. 2015

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Dynamic switching of the vortex circulation in magnetic nanodisks by fast rising magnetic field pulse requires annihilation of the vortex core at the disk boundary and reforming a new vortex with the opposite sense of circulation. Here we study the influence of pulse parameters on the dynamics and efficiency of the vortex core annihilation in permalloy (Ni80Fe20) nanodisks. We use magnetic transmission soft x-ray microscopy to experimentally determine a pulse rise time -pulse amplitude phase diagram for vortex circulation switching and investigate the time-resolved evolution of magnetization in different regions of the phase diagram. The experimental phase diagram is compared with an analytical model based on Thiele's equation describing high amplitude vortex core motion in a parabolic potential. We find that the analytical model is in a good agreement with experimental data for a wide range of disk geometries. From the outputs of the analytical model and in accordance with our experimental finding we determine the geometrical condition for dynamic vortex core annihilation and pulse parameters needed for the most efficient and fastest circulation switching. The comparison of our experimental results with micromagnetic simulations show that the micromagnetic simulations of 'ideal' disks with diameters larger than ∼250 nm overestimate nonlinearities in susceptibility and eigenfrequency. This overestimation leads to the core polarity switching near the disk boundary, which then in disagreement with experimental findings prevents the core annihilation and circulation switching. We modify the micromagnetic simulations by introducing the 'boundary region' of reduced magnetization to simulate the experimentally determined susceptibility and in these modified micromagnetic simulations we are able to reproduce the experimentally observed dynamic vortex core annihilation and circulation switching.

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Section: Introductionmentioning

confidence: 89%

Dynamics and efficiency of magnetic vortex circulation reversal

et al. 2015

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“…Optical probing by means of time-resolved Kerr microscopy has allowed for the measurement of gyrotropic frequency suppression in the presence of naturally occurring pinning sites [6,19,20]. Recent work has begun considering the magnetic-field-induced deformation of the vortex domain structure while it is pinned [21], and indirect experimental evidence for the pinned vortex deformation has been seen [22].…”

Section: Introductionmentioning

confidence: 97%

Magneto-optical imaging of vortex domain deformation in pinning sites

Badea

Frey

Berezovsky

2015

Journal of Magnetism and Magnetic Materials

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a b s t r a c tWe use a sensitive magneto-optical microscopy technique to image the magnetization response of micron-scale ferromagnetic disks to changes in applied magnetic field. This differential technique relies on a modulated applied magnetic field which allows us to measure changes in magnetization 1% < with submicron resolution. The disks are magnetized in single vortex domains, with defects in the material serving to pin the vortex core at particular positions. By applying a small AC magnetic field, we measure the deformation of the magnetization while the core remains pinned. We can also characterize the strength of the pinning site by increasing the AC magnetic field to unpin the vortex core. While pinned, we find that the magnetization away from the core reorients slightly to better align with an applied field. Additionally, an applied field causes the pinned core itself to tilt in the direction of the field. Once the field is large enough to unpin the core, this tilt disappears, and the core instead translates across the disk.

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“…As a matter of fact, vortex walls are nonlocal objects composed of a vortex core and two transverse walls [9][10][11][12], expanding over several exchange lengths in the wire. Because of their spatial extension magnetic vortices are very sensitive to defects and get easily pinned [18][19][20][21]. In contrast, skyrmions are localized objects with a limited expansion from a few tens to one hundred nanometers [8].…”

Section: Introductionmentioning

confidence: 99%

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

2017

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We propose that topological spin currents flowing in topologically nontrivial magnetic textures, such as magnetic skyrmions and vortices, produce an intrinsic nonadiabatic torque of the form T t ∼ [(∂ x m × ∂ y m)·m]∂ y m. We show that this torque, which is absent in one-dimensional domain walls and/or nontopological textures, is responsible for the enhanced nonadiabaticity parameter observed in magnetic vortices compared to one-dimensional textures. The impact of this torque on the motion of magnetic skyrmions is expected to be crucial, especially to determine their robustness against defects and pinning centers.

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Surface Roughness Dominated Pinning Mechanism of Magnetic Vortices in Soft Ferromagnetic Films

Cited by 49 publications

References 22 publications

Dynamics and efficiency of magnetic vortex circulation reversal

Dynamics and efficiency of magnetic vortex circulation reversal

Magneto-optical imaging of vortex domain deformation in pinning sites

Intrinsic nonadiabatic topological torque in magnetic skyrmions and vortices

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