Vortex lattice channeling effects in Nb films induced by anisotropic arrays of mesoscopic pinning centers

Vélez, María; Jaque, D.; Martín, José Ignacio; Montero, Manuel; Schuller, Iván K.; Vicent, J. L.

doi:10.1103/physrevb.65.104511

Cited by 57 publications

(45 citation statements)

References 27 publications

(37 reference statements)

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“…[2][3][4][5][6][7][8][9][10][11][12][13][14] Deep minima develop as a consequence of the geometrical matching between the VL and the underlying periodic structure, which provides the pinning for the VL ͑see Fig. 2͒.…”

Section: Methodsmentioning

confidence: 99%

“…This has allowed experimental exploration of many phenomena regarding static and dynamic properties of the VL. The most remarkable effects arising in this kind of nanostructured superconductors include commensurability between the VL and the periodic array of pinning centers, [2][3][4][5][6][7][8][9][10][11][12] competition between random and periodic pinning, 13 channeling effects in the VL dynamics, 14 or the ratchet effect. 15 Interestingly, much of the physics related to VL dynamics on periodic pinning potentials might apply to other systems in which transport of small particles takes place through fixed periodic potentials, as for instance colloids, 16 electrons in periodic antidot arrays, 17 etc.…”

Section: Introductionmentioning

confidence: 99%

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Vortex-lattice dynamics with channeled pinning potential landscapes

et al. 2005

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We have studied vortex-lattice dynamics as a function of driving force direction, in superconducting Nb films with periodic pinning arrays of magnetic dots. Square and rectangular symmetry arrays define channels that guide the vortex-lattice motion. We investigated the effect of the driving force direction on the commensurability between the vortex-lattice and dots array. We also studied the transverse depinning of the vortexlattice as is moving longitudinally along channels. We found that transverse depinning forces are enhanced with respect to the static situation. The results are discussed in terms of the dynamical evolution of order in the vortex-lattice.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vortex-lattice dynamics with channeled pinning potential landscapes

et al. 2005

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“…12 Therefore, we know, for selected values of the applied magnetic field, how many vortices are per unit cell and where they are, this is, if they are interstitial vortices or vortices in the pinning centers. Other interesting effects induced by these periodic potentials on the vortex lattice behavior are changes in the vortex lattice symmetry, 13 channeling effects in the vortex motion, 14 and effects related to the interplay between these artificial periodic pinning centers and the intrinsic random pinning centers of the sample. 15 Concerning the pinning mechanisms and the magnetic state of the pinning centers, it has been reported 16 that, in our samples ͑Nb thin films with arrays of very thin Ni magnetic pinning centers͒, the pinning mechanisms are the result of the interplay among different magnetic mechanisms.…”

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confidence: 99%

Experimental ratchet effect in superconducting films with periodic arrays of asymmetric potentials

Villegas

González

et al. 2005

Phys. Rev. B

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A vortex lattice ratchet effect has been investigated in Nb films grown on arrays of nanometric Ni triangles, which induce periodic asymmetric pinning potentials. The vortex lattice motion yields a net dc voltage when an ac driving current is applied to the sample and the vortex lattice moves through the field of asymmetric potentials. This ratchet effect is studied taking into account the array geometry, the temperature, the number of vortices per unit cell of the array, and the applied ac currents. DOI: 10.1103/PhysRevB.71.024519 PACS number͑s͒: 74.78.Ϫw, 05.60.Ϫk, 74.40.ϩk Feynman used, in his Lectures on Physics, 1 a ratchet to show how anisotropy never could lead to net motion in an equilibrium system. Since then, asymmetric sawtooth potentials are called ratchet potentials and, in general, a device with broken inversion symmetry is called a ratchet device. The ratchet effect occurs when asymmetric potentials induce outward particle flow under external fluctuations in the lack of any driving direct outward forces. The ratchet effect changes an ac source in a dc one. Ratchet effect spans from Nature phenomena to laboratory fabricated devices. In a ratchet, the energy necessary for net motion is provided by raising and lowering the barriers and wells, either via an external time-dependent modulation, for example an ac current injected in a superconducting film with asymmetric pinning centers, 2 or by energy input from a nonequilibrium source, such as a chemical reaction, as for instance in biological motors. 3 During the past years, ratchet effect has called the attention of many researchers. A state of the art on the related topics Brownian motion and ratchet potential could be found in Ref. 4.The use of ratchetlike pinning potentials in superconductors has been the subject of theoretical approaches which deal with very different topics, for instance, to remove flux trapped in superconducting devices, 5 fluxon optic, 6 logic devices, 7 etc. From the experimental point of view, some progress has been reported related to superconducting circuits, [8][9][10] and very recently vortex motion ratchet effect has been reported in superconducting films with artificially fabricated arrays of asymmetric pinning centers. 2 In the present paper, we will address some of the properties of this superconducting ratchet effect. We will explore the dependence of the ratchet with the applied alternating current, the array shape, the temperature, and the number of vortices per array unit cell. We will show that periodic asymmetric potentials are crucial to produce the ratchet behavior, that the effect is enhanced decreasing the temperature, and finally, that the effect decreases when the applied magnetic field ͑number of vortices per unit cell of the array͒ increases. The paper is organized as follows: First, we will summarize some results on the behavior of vortex lattice on artificially induced pinning potentials. After this, we will present the fabrication method and main characteristics of the films. Finally, the experim...

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“…Despite the need for the complete theoretical understanding of the underlying mechanism that motivates the "SMP", the existence of the accompanying TMI should be studied experimentally in more detail, because the undesirable flux jumps constitute a serious limitation for practical applications. Finally, in the last years many experimental and theoretical works dealt with the change of the superconducting properties of Nb films, when placed in close proximity with arrays of ferromagnetic particles or magnetic homogenous layers [22,23,24,25]. Such composite structures may constitute a starting point for the generation of important electronic devices in the near future [22].…”

Section: Introductionmentioning

confidence: 99%

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

Σταμόπουλος¹,

Speliotis²,

Niarchos³

2004

Supercond. Sci. Technol.

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We report on magnetic and magnetoresistance measurements in two categories of superconducting Nb films grown via magnetron sputtering and MgB−2 bulk samples. In the first category, films of Tc = 9.25 K were produced by annealing during deposition. In these films, the magnetic measurements exhibited the so-called "second magnetization peak" ("SMP"), which is accompanied by thermomagnetic instabilities (TMI). The characteristic field H fj , where the first flux jump occurs, has been studied as a function of the sweep rate of the magnetic field. Interestingly, in the regime T < 6.4 K, the respective line H fj (T ) is constant, H fj (T< 6.4 K)= 40 Oe. A comparison to TMI observed in MgB2 bulk samples is also performed. Our experimental findings can't be described accurately by current theories on TMI. In the second category, films of Tc = 8.3 K were produced without annealing during deposition. In such films, we observed a peak effect (PE). In high magnetic fields the PE is accompanied by a sharp drop and a narrow hysteretic behavior (∆T < 20 mK) in the measured magnetoresistance. In contrast to experimental works presented in the past, the comparison of our magnetic measurements with the magnetoresistance data suggests that rather the appearance of surface superconductivity than the melting transition of vortex matter, is the cause of the observed behavior.

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Vortex lattice channeling effects in Nb films induced by anisotropic arrays of mesoscopic pinning centers

Cited by 57 publications

References 27 publications

Vortex-lattice dynamics with channeled pinning potential landscapes

Vortex-lattice dynamics with channeled pinning potential landscapes

Experimental ratchet effect in superconducting films with periodic arrays of asymmetric potentials

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples

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Vortex lattice channeling effects in Nb films induced by anisotropic arrays of mesoscopic pinning centers

Cited by 57 publications

References 27 publications

Vortex-lattice dynamics with channeled pinning potential landscapes

Vortex-lattice dynamics with channeled pinning potential landscapes

Experimental ratchet effect in superconducting films with periodic arrays of asymmetric potentials

From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB2bulk samples

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From the second magnetization peak to peak effect. A study of superconducting properties in Nb films and MgB₂bulk samples