Anisotropic pinning in Nb thin films with triangular pinning arrays

Cao, Rong; Wu, Tzong‐Chen; Kang, Penghua; Wu, Jong-Ching; Yang, Tsung Hsun; Horng, Lance

doi:10.1016/j.ssc.2007.04.037

Cited by 23 publications

(26 citation statements)

References 10 publications

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“…We have shown also the anisotropy in the critical current and dynamical phases of Kagomé pinning lattice when we apply forces that are mutually perpendicular. This result is in accordance with experimental results [11], and can be explained due to the different interstitial pinning in each case.…”

Section: Resultssupporting

confidence: 92%

“…They have been extensively used to study several physical phenomena and give us the possibility to study some of their unique features [3]. Furthermore, experimental results [11] suggest that when there are interstitial vortices, in superconductors with periodic pinning arrays, the transport properties in two perpendicular directions can be anisotropic. In the present work we analyze the effects of the anisotropy in the critical currents for the Kagomé pinning lattice using two mutually perpendicular directions of transport current and compare with the critical current of the hexagonal lattice.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Pinning on Critical Currents of Superconducting Films

Simões

Venegas

Mello

2012

J Supercond Nov Magn

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-Using molecular dynamics simulations, we analyze the effects of artificial periodic arrays of pinning sites on the critical current of superconducting thin films as a function of vortex density. We analyze two types of periodic pinning arrays: hexagonal and Kagomé. For the Kagome pinning network we calculate, using two directions of transport current: longitudinal and transversal. Our results show that the hexagonal pinning array presents higher critical currents than Kagomé and random pinning configuration for all vortex densities. In addition, the Kagomé network shows anisotropy in their transport properties.

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Section: Resultssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

The Effects of Pinning on Critical Currents of Superconducting Films

Simões

Venegas

Mello

2012

J Supercond Nov Magn

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“…When the transport force is in the y direction and above its critical value, the vortex movement becomes complex, so that in the first dynamical phase, a quarter of the vortices remain trapped and the rest of the vortices move by sinuous channels. Increasing the force causes all of the vortices to move by channels that have interconnectivity resembling the smectic phase found in systems of vortices with random pinning [10]. A further increase in the force causes the vortices to move in well-defined channels over the commensurate rows.…”

Section: Resultsmentioning

confidence: 90%

Critical Currents and Melting Temperature of a Two-Dimensional Vortex Lattice with Periodic Pinning

Verga

Bonilha

Carlone

et al. 2012

J Supercond Nov Magn

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-The critical current and melting temperature of a vortex system are analyzed. Calculations are made for a two dimensional film at finite temperature with two kinds of periodic pinning: hexagonal and Kagomé. A transport current parallel and perpendicular to the main axis of the pinning arrays is applied and molecular dynamics simulations are used to calculate the vortex velocities to obtain the critical currents. The structure factor and displacements of vortices at zero transport current are used to obtain the melting temperature for both pinning arrays. The critical currents are higher for the hexagonal pinning lattice and anisotropic for both pinning arrays. This anisotropy is stronger with temperature for the hexagonal array. For the Kagomé pinning lattice, our analysis shows a multi stage phase melting; that is, as we increase the temperature, each different dynamic phase melts before reaching the melting temperature. Both the melting temperature and critical currents are larger for the hexagonal lattice, indicating the role for the interstitial vortices in decreasing the pinning strength.

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“…Numerical simulations and experiments in triangular lattices have shown that anisotropic transport is a signature of interstitial vortices that find different channels for vortex flow depending on their propagation direction. 22,25 Thus, the existence of a significant anisotropy in the system, together with its dependence on field and temperature ͑i.e., vortex density and pinning strength͒ is, again, a clear signal of the presence of interstitial vortices even at fractional matching conditions. Figure 1͑c͒ shows that vortex motion parallel to the Y axis fulfils the ratchet condition of moving on asymmetric potentials albeit the array is made up of symmetric circular Ni dots.…”

Section: ͑2͒mentioning

confidence: 99%

Vortex ratchet reversal at fractional matching fields in kagomélike array with symmetric pinning centers

et al. 2010

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Arrays of Ni nanodots embedded in Nb superconducting films have been fabricated by sputtering and electron-beam lithography techniques. The arrays are periodic triangular lattices of circular Ni dots arranged in a kagomélike pattern with broken reflection symmetry. Relevant behaviors are found in the vortex lattice dynamics: ͑i͒ at values lower than the first integer matching field, several fractional matching fields are present when the vortex lattice moves parallel or perpendicular to the reflection symmetry axis of the array showing a clear anisotropic character in the magnetoresistance curves, ͑ii͒ injecting an ac perpendicular to the reflection symmetry axis of the array yields an unidirectional motion of the vortex lattice ͑ratchet effect͒ as a result of the interaction between the whole vortex lattice and the asymmetric lattice of dots, ͑iii͒ increasing the input current amplitudes the ratchet effect changes polarity independently of matching field values. These experimental results can be explained taking into account the vortex lattice density.

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Anisotropic pinning in Nb thin films with triangular pinning arrays

Cited by 23 publications

References 10 publications

The Effects of Pinning on Critical Currents of Superconducting Films

The Effects of Pinning on Critical Currents of Superconducting Films

Critical Currents and Melting Temperature of a Two-Dimensional Vortex Lattice with Periodic Pinning

Vortex ratchet reversal at fractional matching fields in kagomélike array with symmetric pinning centers

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