Magnetic vortex dynamics in the presence of pinning

Compton, Robert; Chen, T. Y.; Crowell, P. A.

doi:10.1103/physrevb.81.144412

Cited by 63 publications

(77 citation statements)

References 43 publications

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“…The orbital tilts are sensitive to the relative magnitudes of all three driving contributions: adiabatic, non-adiabatic and Oersted. Hence, mapping the tilt angle with respect to frequency may allow the additional determination of the degree of spin polarization, P, though in practice, local pinning effects can influence low-amplitude oscillations and may complicate the interpretation of P 18,21 .…”

Section: Simulations (See Methods For Details) the Sum Of The Squarementioning

confidence: 99%

“…We carefully tuned the frequency in the experiments until the maximum core trajectory is observed and fit the resonant amplitudes as a function of current for both chiralities to obtain β. Currents were chosen such that the maximum vortex core displacements were only 6.5% of the disc width to prevent anharmonic contributions to the motion, but to still maintain large enough displacements to minimize the pinning effects that are present for static or weakly driven excitations 18,21 . This represents one of the key advantages of our approach, as pinning can lead to large errors 6 .…”

Section: Determination Of mentioning

confidence: 99%

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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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Section: Simulations (See Methods For Details) the Sum Of The Squarementioning

confidence: 99%

Section: Determination Of mentioning

confidence: 99%

Direct dynamic imaging of non-adiabatic spin torque effects

et al. 2012

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“…It is confined to the vortex core (VC) of diameter comparable to the material exchange length 7,8 . Recent experimental works reported evidence that the dynamics of the VC is affected by the presence of structural defects in the sample [9][10][11][12] . This is indicative of the behavior similar to that of the elastic string in a random pinning potential 13 , with the finite elasticity of the vortex provided by the exchange interaction 14 .…”

Section: Introductionmentioning

confidence: 99%

Josephson Junction with a Magnetic Vortex

Zarzuela

Chudnovsky

Tejada

2015

J Supercond Nov Magn

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We have studied Josephson tunneling through a circularly polarized micron or submicron-size disk of a soft ferromagnetic material. Such a disk contains a vortex that exhibits rich classical dynamics and has recently been proposed as a tool to study quantum dynamics of the nanoscale vortex core. The change in the Josephson current that is related to a tiny displacement of the vortex core has been computed analytically and plotted numerically for permalloy disks used in experiments. It is shown that a Josephson junction with a magnetic disk in the vortex state can be an interesting physical system that may be used to measure the nanoscale motion of the magnetic vortex.

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“…Nevertheless, real Permalloy nanowire samples contain defects in their microstructure, e.g., surface roughness and/or grain boundaries, which can act as pinning centers for the domain walls. From experiments [25][26][27][28][29] it is known that these are randomly distributed throughout the wire with a density σ ranging from 690 to 2000 μm −2 , and give rise to a pinning potential for a vortex that is approximately 2 eV deep and has an interaction range roughly equal to the size of the vortex core. In this contribution we numerically investigate the influence of such distributed disorder on the domain wall mobility.…”

Section: Introductionmentioning

confidence: 99%

Influence of material defects on current-driven vortex domain wall mobility

et al. 2014

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Many future concepts for spintronic devices are based on the current-driven motion of magnetic domain walls through nanowires. Consequently a thorough understanding of the domain wall mobility is required. However, the magnitude of the nonadiabatic component of the spin-transfer torque driving the domain wall is still debated today as various experimental methods give rise to a large range of values for the degree of nonadiabaticity. Strikingly, experiments based on vortex domain wall motion in magnetic nanowires consistently result in lower values compared to other methods. Based on the micromagnetic simulations presented in this contribution we can attribute this discrepancy to the influence of distributed disorder which vastly affects the vortex domain wall mobility, but is most often not taken into account in the models adopted to extract the degree of nonadiabaticity.

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Magnetic vortex dynamics in the presence of pinning

Cited by 63 publications

References 43 publications

Direct dynamic imaging of non-adiabatic spin torque effects

Direct dynamic imaging of non-adiabatic spin torque effects

Josephson Junction with a Magnetic Vortex

Influence of material defects on current-driven vortex domain wall mobility

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