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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5117-5124 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the influence of deposition conditions on the structure and properties of Co84Cr14Ta2 alloy magnetic thin films and Cr underlayers sputtered onto circumferentially textured and smooth polished NiP/Al substrates. Suitable processing conditions provide in-plane magnetic anisotropy in the textured media, with enhanced coercivity (Hc) and coercivity squareness (S*) in the circumferential direction and reduced Hc and S* in the radial direction. The crystallography in these films was studied by transmission electron microscopy (TEM) to address the origin of the observed magnetic anisotropy. The CoCrTa alloy grains are found to grow semicoherently on the chromium underlayer, resulting in vertical 〈200(approximately-greater-than) Cr and 〈112¯0(approximately-greater-than) CoCrTa axes. This requires an in-plane orientation of the CoCrTa c axis, which is observed to be nearly random by high-resolution TEM. Microdiffraction shows apparent preferred c-axis alignment locally at texture lines, but this observation is primarily attributable to asymmetric tilting of the vertical growth direction caused by the substrate topography. The 〈112¯0(approximately-greater-than) growth axis appears to be perpendicular to the local grooved surface, not the bulk surface, requiring a local c-axis out-of-plane tilt near the grooves. The anisotropic surface topography induces a corresponding anisotropy in the out-of-plane component of the magnetically easy c axis in the CoCrTa alloy, which we suggest has implications on the bulk magnetic anisotropy in such films.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5542-5544 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Media having Cr-underlayer and NiP-underlayer were compared using transmission electron microscopy (TEM), delta-M, torque (vertical component), and media noise measurements. TEM micrographs show that NiP-underlayer media were more isolated than Cr-underlayer media. Of the Cr-underlayer media, CoCrTa media seem to exhibit grain isolation. The grain size of NiP-underlayer media was smaller (30 nm) than that of Cr-underlayer media (60 nm). Results indicate that media with isolated grains seem to have higher vertical component than media with more continuous grains. The NiP-underlayer media exhibits lower media noise than the Cr-underlayer media. This is attributed to smaller and more isolated grains in the NiP-underlayer media.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5566-5568 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High-resolution transmission-electron microscopy (HRTEM) has been used to analyze CoCrTa, CoCrPt, and CoNiCrPt alloy thin films deposited under similar conditions onto NiP plated Al substrates with a Cr underlayer. Apparent ∼50 nm Co alloy grains observed by bright field TEM are found to be clusters of smaller 10–20 nm grains with a common growth orientation. Subtle differences have also been observed in the stacking fault density, Co alloy fcc phase concentration, lattice mismatch, and grain separation in the films. In particular, HRTEM shows that the CoCrTa film has clear physical separation between the 10 and 20 nm grains, which is not observed in the other media. Despite similar hysteresis loop properties, the signal-to-noise ratio of CoCrTa is 2.3 dB higher than CoCrPt and 4.6 dB higher than CoNiCrPt. Small isolated grains have been shown to improve media noise, as is observed in CoCrTa media.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7505-7507 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We theoretically study the spin-polarized current flowing through a Josephson junction (JJ) in a spin injection device. When the spin-polarized current is injected from a ferromagnet in a superconductor (SC), the charge current is carried by the superconducting condensate (Cooper pairs), while the spin-up and spin-down currents flow in equal magnitude but in the opposite direction in a SC, because of no quasiparticle charge current in the SC. This indicates that not only the Josephson current but also the spin current flow across JJ at zero bias voltage, thereby generating Joule heating by the spin current. The result provides a new method for detecting the spin current by measuring Joule heating at JJ. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 3740-3744 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using c-axis-oriented oxygen-deficient YBa2Cu3O7−δ film deposited across a low-angle step on a SrTiO3 substrate, we successfully demonstrated intrinsic Josephson effects. In addition to several voltage jumps of large amplitudes (a few millivolts) and remarkable hysteresis on the dc current–voltage curves, we observed upturns on the current–voltage curves under microwave irradiation which appeared at increasingly high voltages with increasing microwave power. We proposed to explain this observation in terms of high-order microwave-induced Shapiro steps. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 7675-7677 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We report successful fabrication and characteristics of submicron-size tunneling junctions using c-axis YBa2Cu3O7−y (YBCO) thin films of 800 nm thickness and Bi2Sr2CaCu2O8+δ(Bi-2212) single-crystal whiskers. The junctions were made using a three-dimensional focused-ion-beam etching method. First, a microbridge was patterned in a required junction width by normal direction etching. By tilting the sample stage up to 90°, two grooves on the bridge were etched from the lateral direction in order to create the required junction size. The 60 K YBCO junctions did not show any degradation of critical current density (Jc) down to an in-plane area of 0.5 μm2 and showed current–voltage (I–V) characteristics of the collective switching transition from the zero voltage state to the resistive state. For Bi-2212 stacks smaller than 1 μm2, we identified some of the features of charging effects on the I–V characteristics. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6536-6538 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Following a method proposed by Divin and Modovets [Sov. Tech. Phys. Lett. 9, 108 (1983)], we have measured at millimeter waveband the intrinsic noise temperatures TN of YBa2Cu3O7−δ Josephson junctions or dc superconducting quantum interference devices (SQUIDs) fabricated on SrTiO3, yttria-stabilized ZrO2, or Si bicrystal substrates. Over wide ranges of physical temperatures TP and the junction's normal resistance RN, it was found that TN follows TP pretty well. This indicates that the intrinsic noise in the devices is dominated by Johnson noise. TN was also measured in cases where there is external magnetic field applied, or where there is another microwave radiation like the local oscillator in a mixer. The magnetic field or microwave radiation does not seem to affect TN in any appreciable way. To estimate the high frequency performance of the junctions on Si bicrystal substrates, direct irradiation by a far infrared laser at 1.81 THz is carried out and the clear first Shapiro step is observed. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1895-1898 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied low frequency (1/f) noise of YBa2Cu3O7−δ dc superconducting quantum interference devices (SQUIDs) on SrTiO3 bicrystal substrates. 1/f flux noise, either measured at different temperatures for optimized bias current or measured at 77 K for different bias currents, is almost constant. These facts imply that 1/f noise mainly comes from fluctuations of the critical current of the Josephson junction that form the SQUID. Also, we explain the critical current fluctuations in the junction by an equilibrium temperature fluctuation model.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6144-6146 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetic and noise properties of oriented CoCrTa/Cr media sputtered at temperatures from ambient to 250 °C were studied and correlated with microstructural data from HRSEM and HRTEM micrographs. Coercivity increases monotonically and loop squareness decreases with substrate temperature. Transition and uniform magnetization noise power are highest for media sputtered at 150 °C. Micrographs and noise powers show that the media sputtered at 150 °C is relatively highly exchange-coupled. Media sputtered below 150 °C shows topographic isolation, and those sputtered above 150 °C exhibit increasing intergranular isolation of about 10 A(ring) and thus lower exchange. Coercivity varies linearly but exchange drops abruptly at high temperature. Other mechanisms besides exchange contribute to the coercivity variation.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1169-1171 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Superconducting glass ceramics of Bi0.8Pb0.2SrCaCu1.5Oy (sample A) and BiPb0.2SrCaCu1.5Oy (sample B) have been prepared by using the melt quenching method. It was found that the volume fraction of the high Tc phases in sample A annealed at 830 or 840 °C for 250 h was much higher than that in sample B. The annealed (840 °C, 250 h) sample A exhibited superconductivity with a Tc (zero) of 100 K and a critical current density (77 K, zero magnetic field) of 120 A/cm2.
    Materialart: Digitale Medien
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