Nonlinear flux-line dynamics in vanadium films with square lattices of submicron holes

Metlushko, V.; Welp, U.; Crabtree, G. W.; Zhao, Ziran; Brueck, S. R. J.; Watkins, Byron; DeLong, L. E.; Ilić, B.; Chung, Kee‐Choo; Hesketh, Peter J.

doi:10.1103/physrevb.59.603

Cited by 71 publications

(40 citation statements)

References 30 publications

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“…9,10 We found that blind holes are less efficient pinning centers than antidots. This effect manifests itself as a lower ac shielding and consequently as a smaller extension of the linear regime.…”

Section: Introductionmentioning

confidence: 84%

Flux-pinning properties of superconducting films with arrays of blind holes

et al. 2004

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We performed ac susceptibility measurements to explore the vortex dynamics and the flux-pinning properties of superconducting Pb films with an array of microholes (antidots) and not fully perforated holes (blind holes). A lower ac shielding together with a smaller extension of the linear regime for the lattice of blind holes indicates that these centers provide a weaker pinning potential than antidots. Moreover, we found that the maximum number of flux quanta trapped by a pinning site, i.e., the saturation number n s , is lower for the blind hole array.

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Section: Introductionmentioning

confidence: 84%

Flux-pinning properties of superconducting films with arrays of blind holes

et al. 2004

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“…Non-uniform magnetic fields with nanoscale spatial variations are known to appear in a variety of systems, such as the Abrikosov flux lattice [5] and arrays of nanoscale holes in superconducting films [6]. However, one of the most promising possibilities, which we investigate in this Letter, is provided by the magnetic vortex state [7] of nanoscale magnetic disks of ferromagnetic permalloy Ni 80 Fe 20 , Co or Fe.…”

mentioning

confidence: 96%

Nanoscale Zeeman Localization of Charge Carriers in Diluted Magnetic Semiconductor–Permalloy Hybrids

Berciu

Jankó

2003

Phys. Rev. Lett.

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We investigate the possibility of charge carrier localization in magnetic semiconductors due to the presence of a highly inhomogeneous external magnetic field. As an example, we study in detail the properties of a magnetic semiconductor-permalloy disk hybrid system. We find that the giant Zeeman response of the magnetic semiconductor in conjunction with the highly non-uniform magnetic field created by the vortex state of a permalloy disk can lead to Zeeman localized states at the interface of the two materials. These trapped states are chiral, with chirality controlled by the orientation of the core magnetization of the permalloy disk. We calculate the energy spectrum and the eigenstates of these Zeeman localized states, and discuss their experimental signatures in spectroscopic probes. , below which they exhibit ferromagnetic order. In the ferromagnetic state, the charge carriers are spin-polarized, making these materials ideal sources of spin-polarized currents. To date, most suggested applications involving DMS are based on this property and therefore are restricted to operation in a range of temperatures T ≪ T c . On the other hand, in the paramagnetic phase T > T c both the III 1−x Mn x V and the more established II 1−x Mn x VI DMSs (which have even lower critical temperatures) show giant Zeeman response to external magnetic fields. In our opinion, this can lead to interesting applications in the paramagnetic state, and consequently at rather elevated temperatures.Convincing experimental evidence for Zeeman splitting in the range of 30 meV for external fields of a few Tesla is provided by photoluminesce spectroscopy studies [2]. Even relatively small external magnetic fields of 0.1 − 0.5 T can easily lead to a 15 meV splitting of electronic energy levels [3]. Comparing this to the vacuum Zeeman splitting of ∼ 0.06 meV (for B = 0.5T ) suggests that the effective gyromagnetic ratio of charge carriers in diluted magnetic semiconductors is g > 500. The origin of this hugely enhanced Zeeman effect is attributed [3] to the strong magnetic coupling i J sp−d ( r − R i ) s · S i between the spin s of the charge carrier and the spins S i of the Mn located at R i . In the paramagnetic state, a small magnetic field B induces a magnetization S i ∼ χ B of the Mn spins, resulting in an effective Zeeman-like s · B coupling between the charge carrier spin and the magnetic field, in addition to the regular Zeeman coupling −g 0 µ B s · B present in non-magnetic semiconductors. The scale of this additional coupling is set by the large exchange energy J sp−d and results in a large effective g-value. This also implies that g(T ) has a strong T-dependence through the magnetic susceptibility, and therefore can be tuned over a large range of values. This scenario is strongly supported by magneto-optical absorption measurements [4] of the Zeeman splitting at the band edge, which clearly exhibits a Brillouin-type dependence on the magnetic field.The presence of giant Zeeman response in DMS implies that a moderate external magnetic fi...

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“…Additional depletion can also be attributed to the long range nature of the screening current. 47,48 However, the experimental observation in antidot systems of pronounced matching effects at values of the applied field that coincide with the expected flux-density, µ 0 H = nB 1 , [10][11][12][13][14][15][16][17][18][19][20][21][22] suggests that the depletion zone is much narrower than the sample itself. In any case, as shown in the Supplemental Material, our results do not depend strongly on the width of the fluxdepleted region.…”

Section: 46mentioning

confidence: 99%

“…[10][11][12] This reflects in different (according to whether or not interstitial vortices are present) scenarios of the sample response to an excitation, as indeed observed in a great deal of macroscopic ac-susceptibility experiments. [13][14][15][16][17][18][19][20][21][22] The interpretation of the different dynamical regimes usually ig-nores the random pinning potential produced by sample inhomogeneities, considered negligible at the temperatures where the experiments are carried out. However, at least for experiments performed within the linear regime, where vortices are driven close to their equilibrium positions by very small driving forces, the weak material pinning might become important or even dominant.…”

Section: And References Therein)mentioning

confidence: 99%

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

et al. 2016

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We investigate by scanning susceptibility microscopy the response of a thin Pb strip, with a square array of submicron antidots, to a low-frequency ac magnetic field applied perpendicularly to the film plane. By mapping the local permeability of the sample within the field range where vortices trapped by the antidots and interstitial vortices coexist, we observed two distinct dynamical regimes occurring at different temperatures. At a temperature just below the superconducting transition, T /Tc = 0.96, the sample response is essentially dominated by the motion of highly mobile interstitial vortices. However, at a slightly lower temperature, T /Tc = 0.93, the interstitial vortices freeze up leading to a strong reduction of the ac screening length. We propose a simple model for the vortex response in this system which fits well to the experimental data. Our analysis suggests that the observed switching to the high mobility regime stems from a resonant effect, where the period of the ac excitation is just large enough to allow interstitial vortices to thermally hop through the weak pinning landscape produced by random material defects. This argument is further supported by the observation of a pronounced enhancement of the out-of-phase response at the crossover between both dynamical regimes.

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Nonlinear flux-line dynamics in vanadium films with square lattices of submicron holes

Cited by 71 publications

References 30 publications

Flux-pinning properties of superconducting films with arrays of blind holes

Flux-pinning properties of superconducting films with arrays of blind holes

Nanoscale Zeeman Localization of Charge Carriers in Diluted Magnetic Semiconductor–Permalloy Hybrids

Probing the low-frequency vortex dynamics in a nanostructured superconducting strip

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