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1

Digitale Medien

Giant magnetoresistive memory effect in Nd0.7Sr0.3MnOz (abstract) : The 40th annual conference on magnetism and magnetic materials (1996)

Xiong, G. C. ; Li, Q. ; Ju, H. L. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 79 (1996), S. 5165-5165

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A novel giant magnetoresistance memory effect has been observed in epitaxial Nd0.7Sr0.3MnOz thin films which have previously been found to exhibit a linear increase in conductivity on first application of a magnetic field (B). Here we reported that the conductivity of the films depends not only on the applied field but also on the magnetic history. At T well below the temperature Tp where the zero-field resistivity has a peak, the film enters a high conductivity state [(ΔR/RB)(approximately-greater-than)103] upon application of a magnetic field which persists even when B is reduced to zero. The original "zero'' field state is not recovered until the sample is warmed to T∼Tp. Surprisingly, the dc magnetization exhibits only a weak irreversibility while the magnetoconductivity is markedly hysteretic. That is, while the remanent magnetization is small the remanent magnetic resistivity is 10−3 times the initial zero-field-cooled resistivity. A possible explanation based on a two-component model of semiconducting matrix with embedded shunting paths of ferromagnetic material will be presented. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.361542

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2

Digitale Medien

Giant magnetoresistive memory effect in Nd0.7Sr0.3MnOz films (1995)

Xiong, G. C. ; Li, Q. ; Ju, H. L. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 67 (1995), S. 3031-3033

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A novel giant magnetoresistance memory effect has been observed in epitaxial Nd0.7Sr0.3MnOz thin films which have previously been found to exhibit a linear increase in conductivity on first application of magnetic field B. The resistivity of the films depends not only on the instantaneous applied field but also on the magnetic history of the sample. At T well below the temperature Tp, where the zero-field resistivity has a peak, the film enters a high-conductivity state (upon application of a magnetic field) which persists even when B is reduced to zero. The original "zero'' field state is not recovered until the sample is warmed to T∼Tp. Surprisingly, the dc magnetization exhibits only a weak irreversibility while the magnetoconductivity is markedly hysteretic. A possible explanation is proposed. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.115444

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3

Digitale Medien

Multilayer optics for harmonic control of angiography beamline sources : The 9th National conference on synchrotron radiation instrumentation (1996)

Tatchyn, R. ; Cremer, T. ; Boyers, D. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 67 (1996), S. 3357-3357

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: In recent work, multilayers with band-tailored optics for dual energy digital subtraction angiography (DDSA) applications have been designed and tested at SSRL. Control of various multilayer parameters, including period grading, ratio of high-to-low Z material thickness, number of layers, etc., was used to produce reflectors with bandwidths ranging from 0.6%–10% and efficiencies in the 30%–95% range. In this paper, we consider the control of multilayer bandshapes and the implementation of double-reflection multilayer configurations to further control the first harmonic (33 keV) bandwidth and to suppress or eliminate the 66 keV and 99 keV harmonics present on angiography beamlines driven by wiggler or micropole undulator sources. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1147465

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4

Digitale Medien

Unsteady separation from the leading edge of a thin airfoil (1996)

Degani, A. T. ; Li, Q. ; Walker, J. D. A.

[S.l.] : American Institute of Physics (AIP)

Physics of Fluids 8 (1996), S. 704-714

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ISSN: 1089-7666

Quelle: AIP Digital Archive

Thema: Physik

Notizen: At high Reynolds numbers, the process leading to dynamic stall on airfoils initiates in the leading-edge region. For thin airfoils, the local motion near rounded leading edges can be represented as flow past a parabola and when the mainstream flow is at an angle of attack to the airfoil, a portion of the boundary layer will be exposed to an adverse pressure gradient. Once the angle of attack exceeds a certain critical value, it is demonstrated that unsteady boundary-layer separation will occur in the leading-edge region in the form of an abrupt focused boundary-layer eruption. This process is believed to initiate the formation of the dynamic stall vortex. For impulsively-started incompressible flow past a parabola, a generic behavior is found to occur over a range of angles of attack, and a limit solution corresponding to relatively large angles is found. The separation in the leading-edge region develops in a zone of relatively limited streamwise extent over a wide range of angles of attack. This suggests that localized control measures (such as suction) may possibly be effective at inhibiting separation. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.868856

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5

Digitale Medien

Linear analysis of electromigration-induced void instability in Al-based interconnects (1998)

Hao, T.-H. ; Li, Q.-M.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 83 (1998), S. 754-759

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Void shape changes induced by electromigration pose reliability problems in Al-based interconnects. Recent observations have shown that a rounded void sometimes collapses to a transverse slit in an interconnect with bamboo-like grain structure. This article provides a linear stability analysis for a circular void that is only partially conductive in an otherwise infinite conductive medium. The relation between the inner conductivity (i.e., the conductivity of the medium in the void) and the critical remote electric field intensity, Ecr, for the linear stability of the void is established. It is proven that when the inner conductivity becomes zero, Ecr goes to infinity, and we can look upon the inner conductivity of a vacuum void as zero. That is why the vacuum circular void is linearly stable. It is also shown that when the inner conductivity is very small, the stability of a void is sensitive to it. From the computational results, we know that if the inner conductivity is 0.1% of that outside the void, the Ecr is only twenty times of that for the dislocation loop case. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.366748

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6

Digitale Medien

Investigation of transverse Peltier effect on top-seeded melt textureYBa2Cu3O7−δ (1996)

He, Z. H. ; Ma, Z. G. ; Li, Q. Y. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 3587-3589

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The transverse Peltier effect is investigated on the top-seeded melt texture superconductor YBa2Cu3O7−δ (YBCO). By restricting the heat absorbing or evolving on one of the sample's surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the ab plane and the c axis, |Sab−Sc|, is about 35 μV/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C 235-240, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off-diagonal thermoelectric effect is responsible for the anomalously high laser-induced transient transverse voltage on the oriented YBCO superconducting thin films. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.117215

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7

Digitale Medien

Ultrafast phase dynamics of coherent carriers in GaAs (1998)

Yu, X. Y. ; Luo, Q. ; Li, W. L. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 73 (1998), S. 3321-3323

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Ultrafast phase dynamics of free-induction decay for carriers in bulk GaAs is studied with differential-phase spectroscopy. The instantaneous phase shifts of the free-induction decay with respect to the excitation pulses are extracted from simultaneously recorded laser pulse autocorrelation and free-induction decay in GaAs. Ultrafast phase dynamics during and immediately after the femtosecond pulse excitation are numerically evaluated with optical Bloch equations using pump pulse and semiconductor exciton parameters as input. Good agreement of the theory with experiment is obtained. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.122708

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8

Digitale Medien

Enhancement of the 77 K irreversibility field and critical current density of (Bi,Pb)2Sr2Ca 2Cu3Ox tapes by manipulation of the final cooling rate (1996)

Parrell, J. A. ; Larbalestier, D. C. ; Riley, G. N. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 69 (1996), S. 2915-2917

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: By manipulating the cooling rate from the final heat treatment, we have raised the 77 K, self-field critical current density (Jc) of multifilament (Bi,Pb)2Sr2Ca2Cu3Ox (2223) tapes by a factor of 3, and the irreversibility field (H*) by more than 50%. The Jc of samples cooled in 7.5% O2 from their reaction temperature of 825 °C increased from ∼8 to ∼24 kA/cm2 and H*(77 K) increased from ∼120 to ∼200 mT as the cooling rate was decreased from 5 to 0.016 °C/min. The results unambiguously show that the flux pinning properties of 2223 tapes can be improved by simple changes in wire processing. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.117322

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9

Digitale Medien

Growth morphology and characteristic structure in nanocrystalline Si film of high conductivity (1995)

Wang, L. C. ; Feng, D. ; Epicier, T. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 66 (1995), S. 968-970

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A new type of hydrogenated nanocrystalline Si film with high electronic conductivity is investigated by means of transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Nearly parallel columnar structures with growth orientation along the [110] zone axis of Si are found from cross-sectional TEM images of the film. HRTEM observation reveals that these columns are composed of nanocrystallites (3–6 nm size) and dendritelike growth morphology, while in the region between columns the texture consists of smaller sized (〈3 nm) grains embedded in a hydrogenated amorphous Si. The volume fraction of the crystalline component is about 58% measured by Raman spectroscopy. The conductivity of the film is very high, about 10−1 (Ω cm)−1. It is considered that this is directly related to the characteristic structure of the film. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.113613

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10

Digitale Medien

Influence of preparation on resistivity behavior of epitaxial Nd0.7Sr0.3MnO3−δ and La0.67Ba0.33MnO3−δ thin films (1995)

Xiong, G. C. ; Li, Q. ; Ju, H. L. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 66 (1995), S. 1689-1691

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The influence of sample preparation on the resistivity and magnetoresistance (MR) behavior of doped manganese oxides has been studied. Two systems, Nd0.7Sr0.3MnO3−δ and La0.67Ba0.33MnO3−δ thin films, have been chosen for this study. The former has the largest reported MR ratio at 60 K and the latter has a large MR ratio at room temperature. Two processes, deposition at a high temperature and annealing at a high temperature, have opposite influences on the resistivity behavior of these films. The results suggest that oxygen stoichiometry and diffusion are important factors in causing the behavior observed in doped manganese oxide films. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.113894

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