Magneto-optical investigations of superconductors

Koblischka, Michael Rudolf; Wijngaarden, Rinke J.

doi:10.1088/0953-2048/8/4/002

Cited by 258 publications

(187 citation statements)

References 114 publications

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“…Flux penetration in high-quality single crystals is very regular and textbooklike. 2 Since the thermal stability of vortex motion is inversely proportion to the sample thickness, 44 one would expect very stable behavior for thin films and regular, nonfractal flux penetration. This is indeed occasionally observed, 1,12,13 but the more common behavior is very irregular.…”

Section: Discussion and Simulations Of Fractal Flux Penetrationmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] This behavior is in contrast with the smooth and well-defined flux penetration observed in single crystals 1,2,10-17 and in some thin films. 1,18,19 That the flux penetration in thin films is often more fractal-like than in single crystals is rather surprising since the stability of the flux front should increase for decreasing thickness, and hence be very stable in the thin-film case.…”

Section: Introductionmentioning

confidence: 99%

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Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

et al. 1998

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In this study the role of anisotropy on flux penetration in c-axis epitaxial Tl 2 Ba 2 CuO 6ϩx and YBa 2 Cu 3 O 7Ϫx films is investigated by magneto-optics. We study thin films of Tl 2 Ba 2 CuO 6ϩx on substrates with vicinal angles of 0°͑well-oriented͒, 0.5°, 2.5°, and 4°and YBa 2 Cu 3 O 7Ϫx films as a function of chain-conduction-induced anisotropy. A crossover from fractal to nonfractal flux penetration is observed with increasing anisotropy. Numerical simulations of anisotropic flux motion are compared with experiment. ͓S0163-1829͑98͒05742-7͔

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Section: Discussion and Simulations Of Fractal Flux Penetrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

et al. 1998

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“…[52][53][54][55][56][57] In this measurement, a Bisubstituted ferrimagnetic iron garnet ͑BIG͒ indicator thin film with in-plane magnetization and exhibiting a large Faraday effect was placed in contact with the large face of the sample ͑i.e., perpendicular to the z axis͒. The sample was placed in a Janis, liquid-He optical cryostat attached to the xyz stage of an optical polarizing microscope ͑Olympus BXFM͒ connected to a charge-coupled-device ͑CCD͒ camera.…”

Section: B Measurements In the Crossed-field Configurationmentioning

confidence: 99%

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

et al. 2007

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Crossed-magnetic-field effects on bulk high-temperature superconductors have been studied both experimentally and numerically. The sample geometry investigated involves finite-size effects along both ͑crossed-͒ magnetic-field directions. The experiments were carried out on bulk melt-processed Y-Ba-Cu-O single domains that had been premagnetized with the applied field parallel to their shortest direction ͑i.e., the c axis͒ and then subjected to several cycles of the application of a transverse magnetic field parallel to the sample ab plane. The magnetic properties were measured using orthogonal pickup coils, a Hall probe placed against the sample surface, and magneto-optical imaging. We show that all principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E-J power law and in which the current density flows perpendicularly to the plane within which the two components of magnetic field are varied. The results of this study suggest that the suppression of the magnetic moment under the action of a transverse field can be predicted successfully by ignoring the existence of flux-free configurations or flux-cutting effects. These investigations show that the observed decay in magnetization results from the intricate modification of current distribution within the sample cross section. The current amplitude is altered significantly only if a field-dependent critical current density J c ͑B͒ is assumed. Our model is shown to be quite appropriate to describe the cross-flow effects in bulk superconductors. It is also shown that this model does not predict any saturation of the magnetic induction, even after a large number ͑ϳ100͒ of transverse field cycles. These features are shown to be consistent with the experimental data.

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“…[48][49][50][51][52][53] Due to the giant Faraday rotation EuX films can be applied also for high-resolution magneto-optical imaging of the flux distribution in superconductors. 54 …”

Section: Optical and Magneto-optical Propertiesmentioning

confidence: 99%

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

et al. 2010

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EuTe possesses the centrosymmetric crystal structure m3m of rocksalt type in which the second-harmonic generation is forbidden in electric dipole approximation but the third-harmonic generation ͑THG͒ is allowed. We studied the THG spectra of this material and observed several resonances in the vicinity of the band gap at 2.2-2.5 eV and at higher energies up to 4 eV, which are related to four-photon THG processes. The observed resonances are assigned to specific combinations of electronic transitions between the ground 4f 7 state at the top of the valence band and excited 4f 6 5d 1 states of Eu 2+ ions, which form the lowest energy conduction band. Temperature, magnetic field, and rotational anisotropy studies allowed us to distinguish crystallographic and magnetic-field-induced contributions to the THG. A strong modification of THG intensity for the 2.4 eV band and suppression of the THG for the 3.15 eV band was observed in applied magnetic field. Two main features of the THG spectra were assigned to 5d͑t 2g ͒ and 5d͑e g ͒ subbands at 2.4 eV and 3.15 eV, respectively. A microscopic quantum-mechanical model of the THG response was developed and its conclusions are in qualitative agreement with the experimental results.

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Magneto-optical investigations of superconductors

Cited by 258 publications

References 114 publications

Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

Crossover between fractal and nonfractal flux penetration in high-temperature superconducting thin films

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

Optical third-harmonic spectroscopy of the magnetic semiconductor EuTe

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