Search results

1

Enhancement of Flux Pinning in the Superconductor-Ferromagnet Bilayer Nb(Co/Pd)

100%

Syryanyy Y., Zhu L., Cieplak M., Chien C.

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issue 2

399-401

EN

The magnetometry and the magnetic force microscopy are used to study the influence of the magnetic domain size on the flux pinning in a superconducting/ferromagnetic bilayer (SFB), in which the S layer is niobium and the F layer is a Co/Pd multilayer with perpendicular magnetic anisotropy. The domain size is pre-defined using the angle-dependent demagnetization. The enhancement of pinning is found to be the strongest, up to a factor of 6, for narrow domains and small magnetic fields. This result differs from the behavior observed in the SFB in which the F layer is Co/Pt. The difference may be attributed to the degree of the disorder in the domain pattern.

2

Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

88%

Abal'osheva I., Abal'oshev A., Cieplak M., Zhu L., Chien C.

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issue 2

396-398

EN

The peculiarities of magnetic field penetration in the form of fingering or dendritic instabilities are studied by magneto-optical technique in the niobium films of different thickness. It is observed that the reduction of Nb film thickness reduces the threshold field for instabilities, in agreement with the theoretical predictions. In addition, it is shown that the silver overlayer deposited on the top of Nb film leads also to the enhancement of instabilities, in marked contrast to the effect of gold or aluminum overlayers, which are known to suppress instabilities.

3

Phase Diagram and Activation Energy for Vortex Pinning in Nb/(Co,Pd) Superconductor-Ferromagnet Bilayer

88%

Syryanyy Y., Aleszkiewicz M., Cieplak M., Zhu L., Chien C.

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vol. 126

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issue 4a

A-123-A-127

EN

Using the magnetoresistance measurements we study the phase transition line and the activation energy for vortex pinning in superconductor/ferromagnet bilayer, built of a ferromagnetic Co/Pd multilayer with perpendicular magnetic anisotropy, and a niobium film, with insulating layer in-between to eliminate proximity effect. The domain width is reversibly pre-defined using the angle-dependent demagnetization. We find that the enhancement of the activation energy for vortex pinning by magnetic domains is rather modest, by a factor of about 2.1. We attribute this to large domain width, and large dispersion of the domain width in this bilayer.

4

Vortex Dynamics in Ferromagnetic/Superconducting Bilayers

88%

Cieplak M., Adamus Z., Kończykowski M., Zhu L., Chien C.

Acta Physica Polonica A

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2008

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vol. 114

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issue 1

23-28

EN

The dependence of vortex dynamics on the geometry of magnetic domain pattern is studied in the superconducting/ferromagnetic bilayers, in which niobium is a superconductor, and Co/Pt multilayer with perpendicular magnetic anisotropy serves as a ferrromagnetic layer. Magnetic domain patterns with different density of domains per surface area and different domain size, w, are obtained for Co/Pt with different thickness of Pt. The dense patterns of domains with the size comparable to the magnetic penetration depth (w≥λ) produce large vortex pinning and smooth vortex penetration, while less dense patterns with larger domains (w ≫ λ) enhance pinning less effectively and result in flux jumps during flux motion.

5

Ultrathin Niobium in the Si/Nb/Si Trilayers

76%

Zaytseva I., Abal'oshev O., Dłużewski P., Minikayev R., Cieplak M., Zhu L., Chien C.

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vol. 126

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issue 4a

A-140-A-144

EN

We study magnetotransport properties of the Si/Nb/Si trilayers, in which the thickness of niobium, d, changes from 1.1 nm to 50 nm, while the thickness of Si is fixed at 10 nm. The niobium films are amorphous for d < 4 nm, while in thicker films the alligned polycrystalline grains are formed. We observe that the Hall coefficient changes sign into negative in the films with d < 1.6 nm. We also find that in the ultrathin films the magnetic field induces a transition from the superconducting into a metallic phase with the resistance smaller than the normal-state resistance.

6

Flux Penetration in a Ferromagnetic/Superconducting Bilayer

76%

Adamus Z., Cieplak M., Abal'oshev A., Kończykowski M., Cheng X., Zhu L., Chien C.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

95-98

EN

An array of miniature Hall sensors is used to study the magnetic flux penetration in a ferromagnetic/superconducting bilayer consisting of Nb as a superconducting layer and Co/Pt multilayer with perpendicular magnetic anisotropy as a ferromagnetic layer, separated by an amorphous Si layer to avoid the proximity effect. It is found that the magnetic domains in the ferromagnetic layer create a large edge barrier in the superconducting layer which delays flux penetration. The smooth flux profiles observed in the absence of magnetic pinning change into terraced profiles in the presence of domains.

7

Magnetoresistance of Si/Nb/Si Trilayers

64%

Zaytseva I., Cieplak M., Abal'oshev A., Dluzewski P., Grabecki G., Plesiewicz W., Zhu L., Chien C.

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issue 2

406-408

EN

We study the superconductor-insulator transition in Si/Nb/Si trilayers, in which the thickness of Si is fixed at 10 nm, and the nominal thickness of Nb changes in the range between d = 20 nm down to d = 0.3 nm. The transmission electron microscopy indicates the formation of the mixed Nb-Si layer for small d. Both the thickness-induced, and the magnetic-field induced superconductor-insulator transition is observed. The crossing point of the isotherms at the critical field B_{c} decreases with decreasing d, and it is T-independent at temperatures below 300 mK. At larger fields the weak peak in magnetoresistance appears in some of the films.

8

Vortex Pinning in Ferromagnet/Superconductor Bilayers - the Dependence on the Ferromagnetic Layer and Temperature

64%

Adamus Z., Cieplak M., Abal'oshev A., Berkowski M., Kończykowski M., Cheng X., Shu L., Chien C.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

451-456

EN

The behavior of vortex pinning induced by the magnetic domain reversal is studied in the ferromagnet/superconductor bilayers in which superconducting film is niobium and the ferromagnetic layers are the Co/Pt superlattices with perpendicular magnetic anisotropy. The local magnetic field across narrow ferromagnet/superconductor bilayer stripe is measured using a line of miniature Hall sensors. The pinning is studied for samples with different amount of repeats of Co/Pt superlattice, and as a function of temperature.

9

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer

64%

Cieplak M., Adamus Z., Konczykowski M., Chen X., Byczuk A., Abal'oshev A., Sang H., Chien C.

Acta Physica Polonica A

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2004

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vol. 106

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issue 5

693-698

EN

The local flux profile and the critical current are studied using an array of Hall sensors in a ferromagnetic-superconducting bilayer which consists of niobium film covering ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy. The results indicate about threefold enhancement of the flux pinning in niobium layer caused by the isolated magnetic domains which are created during the magnetization reversal of the Co/Pt multilayer. The geometrical barrier is absent, and the critical current is strongly peaked in close vicinity to the sample center, suggesting that the critical state differs from that predicted by the Bean model.

Refine search results

Enhancement of Flux Pinning in the Superconductor-Ferromagnet Bilayer Nb(Co/Pd)

Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

Phase Diagram and Activation Energy for Vortex Pinning in Nb/(Co,Pd) Superconductor-Ferromagnet Bilayer

Vortex Dynamics in Ferromagnetic/Superconducting Bilayers

Ultrathin Niobium in the Si/Nb/Si Trilayers

Flux Penetration in a Ferromagnetic/Superconducting Bilayer

Magnetoresistance of Si/Nb/Si Trilayers

Vortex Pinning in Ferromagnet/Superconductor Bilayers - the Dependence on the Ferromagnetic Layer and Temperature

Superconducting Pinning by Magnetic Domains in a Ferromagnet-Superconductor Bilayer