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  • 1
    Digitale Medien
    Digitale Medien
    Second harmonic generation as a sensitive technique for estimating Hc1 of high Tc materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1539-1541 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A simple and interesting technique for measuring the Hc1 of the superconducting grains in bulk high Tc superconductor (HTSC) samples is presented herein. This technique takes advantage of interesting history effects observed in the nonlinear magnetic response of HTSC samples. The hysteretic second harmonic magnetization shows sharp structure at low applied fields due to the magnetic flux trapped inside the grains. This feature is used to track the penetration of magnetic field inside the superconducting granular regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354049
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  • 2
    Digitale Medien
    Digitale Medien
    Flux pinning and dissipation in textured multifilamentary (Bi–Pb)2Sr2Ca2Cu3Ox/Ag tapes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3861-3867 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the magnetotransport, magnetization properties, and microstructure of multifilamentary (Bi–Pb)2Sr2Ca2Cu3Ox (Bi-2223)/Ag tapes with varying filaments from 1 to 37 to explore the energy dissipation, reversible flux motion, and flux pinning related to the microstructure. Our results show that the dissipation is temperature, current, and magnetic field induced. The dissipation is thermally activated and the vortex liquid state is plastically deformed. The dissociation of vortex–antivortex pairs by current, magnetic field, and temperature plays a major role in enhancing the dissipation process, resulting in large broadening in the transition. We observed a reversible fluxoid motion of vortices. The critical current density follows an exponential dependence on the magnetic field. The weak links seem to be broken even for a field as low as 5 G even 12 K below the transition temperature. However, at low temperature, the weak links behave as superconducting. The microscopic characterizations show evidence for the dislocations, stacking faults, and misorientation of grains and grain boundaries that control the critical current in tapes. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1353560
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  • 3
    Digitale Medien
    Digitale Medien
    Flux pinning in melt-processed ternary (Nd–Eu–Gd)Ba2Cu3Oy superconductors with Gd2BaCuO5 addition (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 5705-5711 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The flux pinning behavior of ternary melt-processed (Nd–Eu–Gd)Ba2Cu3Oy superconductors is studied with varying Gd2BaCuO5 second-phase (Gd-211) defect concentrations using magnetotransport and magnetization measurements. The critical current density, Jc increases with the addition of Gd-211 particles displaying a maximum value of Jc for 30% at zero and in intermediate field range and decreases on further addition of Gd-211 particles. A pronounced field-induced bump feature in the resistivity was observed. The dynamic scaling of the resistance suggests the low temperature phase as the vortex-glass phase. The current–voltage characteristics over the whole transition temperature regime show a linear flux–flow type behavior that favors the phenomenon of vortex entanglement in the liquid phase. The Nd/Ba substitution sites along with Gd-211 second-phase particles refined by the addition of a small amount of Pt are one of the possible reasons for the vortex entanglement in the liquid phase. The in-plane and out-of-plane resistance measurements clearly show the correlation of the vortices in the liquid state favoring some influence of twin planes and occasionally occurring natural grain boundaries on the liquid state as well. These defects give rise to high critical current density at low temperature with significant enhancement in pinning favoring the glassy phase to occur. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.371582
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  • 4
    Digitale Medien
    Digitale Medien
    Evidence of strong flux pinning in melt-processed ternary (Nd–Eu–Gd)Ba2Cu3Oy superconductors (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 253-255 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The flux pinning behavior of ternary melt-processed (Nd–Eu–Gd)Ba2Cu3Oy superconductors is studied with varying defect concentrations using magnetotransport and magnetization measurements. A huge field-induced bump feature in the resistivity with increasing defect density, field-induced magnetization kink and linear voltage-current (V-I) characteristics over the whole transition temperature regime favor the phenomenon of vortex entanglement in the liquid phase. The Nd/Ba substitution sites along with the fine second-phase particles are one of the possible reasons for the vortex entanglement and these defects give rise to high critical current density and reduced dissipation at low temperature with significant enhancement in pinning. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.124339
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  • 5
    Digitale Medien
    Digitale Medien
    Flux pinning in ternary (Nd–Eu–Gd)Ba2Cu3O7−δ: Optimization for the highest pinning (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2033-2035 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The optimization of high-quality melt-processed ternary (Nd–Eu–Gd)Ba2Cu3O7−δ composite samples has been carried out to achieve the largest pinning. Our results suggest that the interaction between the twin planes and the fine second-phase precipitate forms a strongly pinned entangled vortex liquid in which vortices are correlated along the c axis. This pinned vortex liquid freezes into a glassy state at low temperature rendering high critical current density, Jc. The maximum Jc can be achieved in as-grown optimally annealed twinned sample with second phase precipitate without disturbing the twin influence. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1312863
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  • 6
    Digitale Medien
    Digitale Medien
    Colossal magnetoresistance in doped manganites: A consequence of percolation and phase separation (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 506-508 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report measurements of the resistivity and magnetization of high-quality melt-processed La0.67Ca0.33MnO3 (LCM) and Sr-doped LCM materials that exhibit a sharp and enhanced metal–insulator transition (TMI) with significant colossal magnetoresistance (CMR) and two competing magnetic phases in the vicinity of TMI. Our results can well be explained using percolation in combination with the phase-separation scenario proposed for CMR. We propose that the spin polarization through grain boundaries and the enhanced grain connectivity between the ferromagnetic domains facilitate better percolation through a junction and filament-like resistor network. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1388158
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  • 7
    Digitale Medien
    Digitale Medien
    Enhanced metal–insulator transition and magnetoresistance in melt-processed La0.67Ca0.33MnO3 and Ho-doped manganites (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 1598-1600 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report significant enhancement of magnetoresistance (MR) in melt-processed La0.67Ca0.33MnO3 (LCM) and in Ho-doped LCM samples. The LCM system exhibits surprising enhancement of metal–insulator transition (TIM) that coincides with the Curie transition temperature (Tc), TIM(approximate)Tc, illustrating the enhanced percolative transport and spin-polarization through grain boundaries. Surprisingly, 1 mol % of addition of Ho enhances Tc of ∼70 K with remarkable colossal MR. The nanoscale Ho distribution is consistent with the magnetic inhomogeneity-induced MR due to phase segregation in Ho-doped sample whereas charge-segregation picture is valid for undoped LCM. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1354659
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  • 8
    Digitale Medien
    Digitale Medien
    Transport behavior and critical current densities in MgB2 wires (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1649-1651 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report on the transport and magnetization properties of MgB2 wires fabricated by a powder-in-tube (PIT) technique. Temperature and magnetic-field-dependent resistivity displays a high conductivity and upper critical field Hc2 generally observed in dense samples. The electronic mass anisotropy γ(approximate)1.3±0.15 predicts some texturing in the wire. Our data on transition temperature TC, Hc2, and both magnetic and transport critical current density Jc indicate that MgB2 can be manufactured in a wire form using a PIT technique and required engineering Jc can be achieved on further optimization. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1403278
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  • 9
    Digitale Medien
    Digitale Medien
    Enhanced room-temperature magnetoresistance in partially melted La0.67Ca0.33MnO3 manganites (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 763-765 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have performed magnetic and transport measurements on La0.67Ca0.33MnO3 polycrystalline and partially melted samples. The magnetization and resistance decrease as sintering temperature is increased. The insulator-to-metal transition temperature is remarkably enhanced in the partially melted sample, enabling its possible applications at room temperature. The microscopic studies in melt samples show an excellent connectivity between grains, suggesting the enhancement of percolative transport by opening new conduction channels and the disappearance of magnetic phase boundary at elevated temperature by the ordering of Mn spins blocked at the grain boundary of sintered samples. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.125887
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  • 10
    Digitale Medien
    Digitale Medien
    Identification of a Stable Maintainer Line for ‘Polima’ Cytoplasmic Male Sterility in Rapeseed (B. napus L.) (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 110 (1993), S. 0 
    Details
    ISSN: 1439-0523
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: ‘Polima’ cytoplasmic male sterility (CMS) was transferred to three different genotypes of B. napus i.e. GSL-1, ISN706 and HNS-8 by repeated backcrossing and was found to be completely stable in the nuclear background of synthetic B. napus genotype, ISN706, derived from a cross B. campestris ssp. oleifera var. brown sarson ×B. oleracea var. botrytis cv. Tusa Katki'. The BC5 and BC6 generation lines of ISN706, GSL-1 and HNS-8 with ‘Polima’ CMS were grown under a range of temperature and photo-period conditions to test their stability. No breakdown in sterility was observed in ‘Polima’ ISN706 and, therefore, this genotype can be used as a maintainer for hybrid seed production.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1439-0523.1993.tb00598.x
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