Inductance measurements of HTSC films with high critical currents

Mikheenko, P.; Kuzovlev, Yu. E.

doi:10.1016/0921-4534(93)91004-f

Cited by 271 publications

(143 citation statements)

References 8 publications

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“…It means that in the case we have considered, the laser pulse redistributes currents signi¯cantly without changing the total number of current vortices in the¯lm. This is in agreement with Maxwell equations, but this fact leads to the conclusion that the current values in large regions of the¯lm were much less than the critical current J c that should be present everywhere in the¯lm under conditions of saturated magnetization in the strong external magnetic¯eld [13].…”

Section: E® Ect Of Laser Pulse Irradiation On Current Distributionsupporting

confidence: 68%

“…It leads to the conclusion that the measured current peculiarities could be considered normal. Hence the near-center current distribution in the case considered here di®ers from the extended Bean model [13] distribution. According to Mikheenko et al [13], the size of the funnel around the center of rotation of the current at our measurement conditions should be about 2{3 microns.…”

Section: Numerical Modellingmentioning

confidence: 99%

“…Hence the near-center current distribution in the case considered here di®ers from the extended Bean model [13] distribution. According to Mikheenko et al [13], the size of the funnel around the center of rotation of the current at our measurement conditions should be about 2{3 microns. The possible explanation of this e®ect is the existence of a long-range interaction between vortices in thin¯lms.…”

Section: Numerical Modellingmentioning

confidence: 99%

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Magnetic field and currents in HTSC films

2003

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Magnetic eld measurements above type-II superconductor lms in a remanent magnetization state have been used to determine two dimensional surface current distributions. Using the Biot-Savart law for the surface current density, integral equations (of 2-D convolution type) for two components of current have been obtained. These equations have been solved by employing Tikhonov's method of generalized discrepancy, and the surface current pattern in superconductors as well as the magnetic eld distribution on the lm surface have been obtained. Current peculiarities related to various kinds of inhomogeneities, speci c character of the lm form, and a laser pulse e¬ect have been observed. In particular, it was discovered that a laser pulse can signi cantly redistribute the lm currents without changing the total number of current vortices in the lm.

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Section: E® Ect Of Laser Pulse Irradiation On Current Distributionsupporting

confidence: 68%

Section: Numerical Modellingmentioning

confidence: 99%

Section: Numerical Modellingmentioning

confidence: 99%

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Magnetic field and currents in HTSC films

2003

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“…[10][11][12][13][27][28][29][30][31][32] The most remarkable difference is that shielding currents flow along the entire width of the sample including the flux-free region whereby the field component perpendicular to the surface is equal to zero. Direct magnetooptical observations of the flux distributions in wide superconducting strips subjected to an external field 33 or carrying a transport current 34 and current distributions extracted from such data 35 are in good agreement with theoretical predictions.…”

Section: Partly Flux-filled Hard Superconductor Strips In a Flat mentioning

confidence: 99%

Overcritical states of a superconductor strip in a magnetic environment

2000

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A current-carrying superconducting strip partly penetrated by magnetic flux and surrounded by a bulk magnet of high permeability is considered. Two types of samples are studied: those with critical current controlled by an edge barrier dominating over the pinning, and those with high pinning-mediated critical current masking the edge barrier. It is shown for both cases that the current distribution in a central flux-free part of the strip is strongly affected by the actual shape of the magnetic surroundings. Explicit analytical solutions for the sheet current and self-field distributions are obtained which show that, depending on the geometry, the effect may suppress the total loss-free transport current of the strip or enhance it by orders of magnitude. The effect depends strongly on the shape of the magnet and its distance to the superconductor but only weakly on the magnetic permeability.

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“…Assuming that the JPR is absent from the field penetrated region of the film, the spectra are just linear combinations of the zero field spectrum and the featureless high field spectrum. One can make this quantitative using the result of Mikheenko and Kuzovlev [18] for the distance a from the center of the disk that is penetrated by the magnetic field: a = R/ cosh(H/(2πj ab c d)), where R is the radius of the disk, H is the applied field, j ab c is the ab-plane critical current and d is the thickness of the film. From comparison to Fig.…”

Section: 72-h7425gzmentioning

confidence: 99%

Effects of Vortex Pinning and Thermal Fluctuations on the Josephson Plasma Resonance inTl2Ba2CaCu2
Dulić
¹
,
Hak
²
,
Marel
³

et al. 2001
Phys. Rev. Lett.
23
0
20
0
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Infrared spectroscopy has been used to investigate the temperature dependence and c-axis magnetic field dependence of the Josephson plasma resonance in optimally doped Tl2Ba2CaCu2O8 thin films, and underdoped YBa2Cu3O6.5 ortho -II single crystals. The resonances are directly related to the c-axis penetration depths, yielding low temperature, zero fields values of about 20 µm, and 7 µm respectively. While the temperature dependencies of the resonances in the two compounds are very similar, the magnetic field dependence in YBCO is much weaker. We attribute this weak magnetic field dependence to the lower anisotropy of YBCO, and discuss the observed behaviours in terms of thermal fluctuations and pinning of pancake vortices, valid for highly anisotropic layered superconductors. 74.25.Gz The Josephson plasma resonance (JPR) phenomenon [1][2][3] provides direct information about the Josephson coupling between the CuO 2 planes in the highly anisotropic high T c superconductors [4]. Studies of the temperature and magnetic field dependence of the JPR provide useful insights into the pinning and thermal fluctuations of vortices in the cuprate family [5][6][7][8][9][10]. It is natural, to anticipate unusual magnetic field behavior in these highly anistropic materials. Indeed, just as in any conventional type-II superconductor, if a DC magnetic field is applied perpendicular to the 2D planes it penetrates the sample in the form of vortices which, when the anisotropy is large, are not vortex lines but pancake vortices. For low magnetic fields and low temperatures, these pancake vortices may form a nearly perfect vortex lattice. Under these conditions there should be no magnetic field dependence of the JPR since ω 2 p (B, T ) = ω 2 p (0) cos(φ n,n+1 )(r) , where ω 2 p (0) is the plasma frequency in zero field, and φ n,n+1 (r) is the gauge-invariant phase difference between the neighboring layers n and n + 1 [8]. In zero field, φ n (r) is independent of r and independent of n for zero c-axis current. In non-zero field, φ n (r) becomes position dependent but φ n,n+1 (r) is everywhere zero, provided the vortex cores are lined up, as in a perfect lattice. However, due to the effects of pinning (at low temperatures), and thermal fluctuations (at higher temperatures) pancake vortices do not in general line up from layer to layer. Both regimes have been extensively studied theoretically by Bulaevskii and one of us (AEK) [9][10][11], but there is very little data on the JPR in the low magnetic field regime [7]. In this paper we present our studies of the temperature and field dependence of the JPR in two members of the high T c family with differing anisotropies.Two types of reflectivity spectra were measured, each optimized to the type of sample: First normal incidence reflectivity spectra were recorded of a mosaic made of six ac-oriented single crystals of YBa 2 Cu 3 O 6.5 with ortho-II oxygen ordering, and a superconducting transition temperature of 58K. The mosaic was held together with epoxy and had an area of 6mm 2 . Second...

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Inductance measurements of HTSC films with high critical currents

Cited by 271 publications

References 8 publications

Magnetic field and currents in HTSC films

Magnetic field and currents in HTSC films

Overcritical states of a superconductor strip in a magnetic environment

Effects of Vortex Pinning and Thermal Fluctuations on the Josephson Plasma Resonance inTl2Ba2CaCu2
Dulić
¹
,
Hak
²
,
Marel
³

et al. 2001
Phys. Rev. Lett.
23
0
20
0
View full text Add to dashboard Cite

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Inductance measurements of HTSC films with high critical currents

Cited by 271 publications

References 8 publications

Magnetic field and currents in HTSC films

Magnetic field and currents in HTSC films

Overcritical states of a superconductor strip in a magnetic environment

Effects of Vortex Pinning and Thermal Fluctuations on the Josephson Plasma Resonance inTl2Ba2CaCu2Dulić1, Hak2, Marel3 et al. 2001Phys. Rev. Lett.230200View full textAdd to dashboardCite

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Effects of Vortex Pinning and Thermal Fluctuations on the Josephson Plasma Resonance inTl2Ba2CaCu2
Dulić
¹
,
Hak
²
,
Marel
³

et al. 2001
Phys. Rev. Lett.
23
0
20
0
View full text Add to dashboard Cite