Flux pinning by regular arrays of ferromagnetic dots

Bael, M. J. Van; Look, Lieve Van; Temst, Kristiaan; Lange, M.; Bekaert, Joost; May, Ulrich; Güntherodt, G.; Moshchalkov, Victor; Bruynseraede, Y.

doi:10.1016/s0921-4534(99)00637-1

Cited by 59 publications

(63 citation statements)

References 14 publications

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“…Motivated by recent experiments 14,15 , we study the properties of a superconducting disk in the presence of a step-like external magnetic field. The step-like field profile is a model magnetic field profile for a ferromagnetic dot or current loop placed on top of the superconductor.…”

Section: Introductionmentioning

confidence: 99%

“…Previous investigations of structures with magnetic dots were limited to experiments with superconducting films deposited on regular arrays of magnetic dots [14][15][16] and theoretical studies of single magnetic dots embedded in a thin superconducting film 17,18 . The common problem was that, for magnetic dots, the strong field present inside the ferromagnet suppresses the superconducting order parameter, and in such situations it is appropriate to adopt a boundary condition in which the order parameter itself vanishes.…”

Section: Introductionmentioning

confidence: 99%

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Vortex structure of thin mesoscopic disks in the presence of an inhomogeneous magnetic field

2002

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The vortex states in a thin mesoscopic disk are investigated within the phenomenological Ginzburg-Landau theory in the presence of different "model" magnetic field profiles with zero average field which may result from a ferromagnetic disk or circulating currents in a loop near the superconductor. We calculated the dependences of both the ground and metastable states on the magnitude and shape of the magnetic field profile for different values of the order parameter angular moment, i.e. the vorticity. The regions of existence of the multi-vortex state and the giant vortex state are found. We analysed the phase transitions between these states and studied the contribution from ring-shaped vortices. A new transition between different multi-vortex configurations as the ground state is found. Furthermore, we found a vortex state consisting of a central giant vortex surrounded by a collection of anti-vortices which are located in a ring around this giant vortex. The limit to a disk with an infinite radius, i.e. a film, will also be discussed. We also extended our results to "real" magnetic field profiles and to the case in which an external homogeneous magnetic field is present.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Vortex structure of thin mesoscopic disks in the presence of an inhomogeneous magnetic field

2002

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“…After substantial progress in the preparation of regular magnetic arrays on superconductors 4 and considering the importance of such structures for magnetic device and storage technologies, these hybrid systems became very interesting both from a theoretical and an experimental point of view. Macroscopic pinning phenomena have already been explored experimentally, [4][5][6] but a theoretical analysis of the magnetic and superconducting response in such systems is still lacking. In the majority of recently proposed models 7-11 the inhomogeneous magnetic field of a ferromagnet induces screening currents in a SC, which, in turn, generate a magnetic field influencing the applied field.…”

Section: Introductionmentioning

confidence: 99%

Magnetic pinning of vortices in a superconducting film: The (anti)vortex-magnetic dipole interaction energy in the London approximation

2002

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The interaction between a superconducting vortex or antivortex in a superconducting film and a magnetic dipole with in-or out-of-plane magnetization is investigated within the London approximation. The dependence of the interaction energy on the dipole-vortex distance and the film thickness is studied and analytical results are obtained in limiting cases. We show how the short range interaction with the magnetic dipole makes the co-existence of vortices and antivortices possible. Different configurations with vortices and antivortices are investigated. 74.60.Ge, 74.25.Dw, 74.25.Ha

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“…This new field compensation effect is not restricted to specific superconductors, so that FIS could be achieved in any superconducting film with a lattice of magnetic dots. To implement the idea of the nanoengineered FIS, we have prepared a sample, which reminds us of other systems used during the last decade for studying flux pinning by periodic arrays of magnetic dots [7,8,9,10,11], and by magnetic domains [12]. The sample consists of a 85 nm superconducting Pb film evaporated on a 1 nm Ge base layer on an amorphous Si/SiO 2 substrate, which is held at liquid nitrogen temperature during deposition.…”

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confidence: 99%

Nanoengineered Magnetic-Field-Induced Superconductivity

et al. 2003

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The perpendicular critical fields of a superconducting film have been strongly enhanced by using a nanoengineered lattice of magnetic dots (dipoles) on top of the film. Magnetic-field-induced superconductivity is observed in these hybrid superconductor / ferromagnet systems due to the compensation of the applied field between the dots by the stray field of the dipole array. By switching between different magnetic states of the nanoengineered field compensator, the critical parameters of the superconductor can be effectively controlled. When the applied magnetic field exceeds a certain critical value, superconductivity is suppressed due to orbital and spin pair breaking effects. This very general property of superconductors sets strong limits for their practical applications, since, in addition to applied magnetic fields, the current sent through a superconductor also generates magnetic fields, which can lead to a loss of zero resistance. Materials that are not only able to withstand magnetic fields, but in which superconductivity can even be induced by applying a magnetic field, are very rare and up to now only (EuSn)Mo 6 S 8 [1, 2], organic λ-(BETS) 2 FeCl 4 materials [4,5] and HoMo 6 S 8 [3] show this unusual behavior. The appearance of magnetic-fieldinduced superconductivity (FIS) in the former two compounds was interpreted in terms of the Jaccarino-Peter effect [6], in which the exchange fields from the paramagnetic ions compensate an applied magnetic field, so that the destructive action of the field is neutralized. Here we report that FIS can also be realized in hybrid superconductor / ferromagnet nanostructured bilayers. The basic idea is quite straightforward (see Fig. 1): a lattice of magnetic dots with magnetic moments aligned along the positive z-direction is placed on top of a superconducting film. The magnetic stray field of each dot has a positive z-component of the magnetic induction B z under the dots and a negative one in the area between the dots. Added to a homogeneous magnetic field H, see Fig. 1(b), these dipole fields enhance the z-component of the effective magnetic field µ 0 H ef f = µ 0 H + B z in the small area just under the dots and, at the expense of that, reduce H ef f everywhere else in the Pb film, thus providing the condition necessary for the FIS observation. This new field compensation effect is not restricted to specific superconductors, so that FIS could be achieved in any superconducting film with a lattice of magnetic dots. To implement the idea of the nanoengineered FIS, we have prepared a sample, which reminds us of other systems used during the last decade for studying flux pinning by periodic arrays of magnetic dots

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Flux pinning by regular arrays of ferromagnetic dots

Cited by 59 publications

References 14 publications

Vortex structure of thin mesoscopic disks in the presence of an inhomogeneous magnetic field

Vortex structure of thin mesoscopic disks in the presence of an inhomogeneous magnetic field

Magnetic pinning of vortices in a superconducting film: The (anti)vortex-magnetic dipole interaction energy in the London approximation

Nanoengineered Magnetic-Field-Induced Superconductivity

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