Magnetostatic interactions between magnetic arrays and superconducting thin films

Otani, Y.; Pannetier, B.; Nozières, J. P.; Givord, D.

doi:10.1016/0304-8853(93)90705-7

Cited by 124 publications

(85 citation statements)

References 4 publications

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“…For instance, in the experiments with arrays of magnetic dots with permanent magnetization placed on top of superconducting Nb films, reported in Ref. [15], d = 20nm ∼ ξ. The magnetic dots are separated from the film by a thin protective layer of thickness ∼ 20nm, so that the distance from the magnetic dipole to the film is z 0 ∼ ξ.…”

Section: Discussionmentioning

confidence: 99%

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Carneiro

2005

Physica C: Superconductivity

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The ratchet effect is demonstrated theoretically for the simple model of a vortex in a thin superconducting film interacting with a periodic array of magnetic dipoles placed in the vicinity of the film . The pinning potential for the vortex is calculated in the London limit and found to break spatial inversion symmetry and to depend on the orientation of the magnetic dipole moments. The motion of the vortex at zero temperature driven by a force oscillating periodically in time is investigated numerically. Drift vortex motion consisting of displacements by a translation vector of the dipole array during each period of oscillation is obtained and studied in detail. The direction of drift differs in general from that of the driving force, except if the driving force oscillates in a direction of high symmetry of the dipole array. The vortex drift velocity depends on the orientation of the magnetic moments, and can be tuned by rotating the dipoles. It is pointed out that if the magnetic moments are free to rotate, the ratchet effect can be produced and tuned by a magnetic field applied parallel to the film surfaces.

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Section: Discussionmentioning

confidence: 99%

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Carneiro

2005

Physica C: Superconductivity

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confidence: 99%

“…To enhance j c , vortex motion must be prevented. The latter can be achieved by introducing different pinning centers such as defects created by ion [1] or neutron irradiation [2], lithographically introduced holes [3,4,5], or magnetic dots [6,7,8,9].Recently it was proposed that vortices in a superconductor/ferromagnet (SC/FM) multilayer are strongly pinned if the FM has a stripe domain structure, which typically exists in thin magnetic films with perpendicular anisotropy [10]. Enhanced pinning was observed in SC/FM bilayers compared to SC reference films [11,12].…”

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confidence: 99%

Magnetic-domain-controlled vortex pinning in a superconductor/ferromagnet bilayer

Lange¹,

Bael²,

Moshchalkov³

et al. 2002

Applied Physics Letters

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Vortex pinning in a type-II superconducting Pb film covering a Co/Pt multilayer with perpendicular magnetic anisotropy is investigated. Different stable magnetic domain patterns like band and bubble domains can be created in the Co/Pt multilayer, clearly influencing the vortex pinning in the superconducting Pb layer. Most effective pinning is observed for the bubble domain state. We demonstrate that the pinning properties of the superconductor/ferromagnet bilayer can be controlled by tuning the size, density and magnetization direction of the bubbles.Magnetic flux penetrates type-II superconductors in the form of quantized vortices, which have the tendency to form a periodic lattice. These vortices move when a current is sent through the superconductor, thus causing dissipation and limiting the critical current density j c of the superconductor. To enhance j c , vortex motion must be prevented. The latter can be achieved by introducing different pinning centers such as defects created by ion [1] or neutron irradiation [2], lithographically introduced holes [3,4,5], or magnetic dots [6,7,8,9].Recently it was proposed that vortices in a superconductor/ferromagnet (SC/FM) multilayer are strongly pinned if the FM has a stripe domain structure, which typically exists in thin magnetic films with perpendicular anisotropy [10]. Enhanced pinning was observed in SC/FM bilayers compared to SC reference films [11,12]. However, in these studies the domain structure of the FM was unknown. In this Letter, we systematically investigate the influence of the domains in a ferromagnetic Co/Pt multilayer with perpendicular anisotropy on a type-II superconducting Pb film grown on top of the FM. Stable domain structures can be produced in a controlled way by magnetizing the sample before measuring the superconducting properties of the Pb film. We show that the strongest vortex pinning is obtained when localized domains (bubble domains) are present in the FM, and that by changing size and density of the bubbles one can control and optimize the vortex pinning.The Co/Pt multilayer is deposited on a Si substrate with amorphous SiO 2 top layer in an MBE apparatus by e-beam evaporation. The multilayer has a [Co(0.4 nm)/Pt(1.0 nm)] 10 structure on a 2.8 nm Pt base layer. A 10 nm Ge film, a Pb film with thickness d P b = 50 nm and a 30 nm Ge capping layer are subsequently evaporated on the Co/Pt multilayer (see Fig. 1) at a substrate temperature of 77 K. The Pb film has a critical temperature of T c = 7.23 K. The penetration depth λ(0) = 42 nm and the coherence length ξ(0) = 41 nm are estimated from measurements of the temperature dependence of the upper critical field. The Ge film between Pb and Co/Pt is insulating at low temperatures, so that the proximity effects between Pb and Co/Pt are suppressed.The Co/Pt multilayer has perpendicular magnetic anisotropy [13], which is confirmed by hysteresis loop (Fig. 3). measurements using the magneto-optical Kerr effect (MOKE). Fig. 2 shows the magnetization M f m of the Co/Pt multilayer, normalized...

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“…Different techniques for creating vortex pinning were proposed, including thickness modulation [1], columnar defects [2] and introduction of magnetic particles on the superconducting film [3,4]. Most of those techniques were based on local suppression of the superconducting state, since it is favorable for the vortex normal core to be located in areas which are normal anyway; hence saving the condensation energy.…”

Section: Introductionmentioning

confidence: 99%

Suppression of the superconducting critical current of Nb in bilayers of Nb∕SrRuO3

Feigenson

Klein

Karpovski

et al. 2005

Journal of Applied Physics

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In bilayers consisting of ferromagnetic and superconducting films, the ferromagnetic film in its domain state induces inhomogeneous distribution of magnetic fields in the superconducting film. When the ferromagnetic film has bubble magnetic domains in a labyrinth structure, it has been found that the pinning of the vortices increases; hence, the critical current of the superconducting film becomes larger. Here we study the effect of parallel ferromagnetic domain structure in Nb/SrRuO 3 on the critical current of Nb with current flowing perpendicularly to the domains and find that in this case the ferromagnetic domain structure decreases the critical current.

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Magnetostatic interactions between magnetic arrays and superconducting thin films

Cited by 124 publications

References 4 publications

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Tunable ratchet effects for vortices pinned by periodic magnetic dipole arrays

Magnetic-domain-controlled vortex pinning in a superconductor/ferromagnet bilayer

Suppression of the superconducting critical current of Nb in bilayers of Nb∕SrRuO3

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