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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1348-1352 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Microstructure and magnetic properties of Mn-Al multilayered films are studied by high-resolution transmission electron microscopy (TEM), x-ray diffraction, and vibrating sample magnetometry to investigate the origin of ferromagnetism. High-resolution TEM images show that the Mn-Al interface is sharp and that the crystal lattice is continuous across the interface. The possibility of ferromagnetic alloy formation is ruled out for explaining the origin of ferromagnetism. The magnetic measurements are made on films with various layer thicknesses and numbers of layers. The saturation magnetization increased as the number of interfaces increased. Magnetic anisotropy differs between films with odd and even numbers of layers. These results suggest that the ferromagnetic regions are located around the Mn-Al interfaces, where large strain and/or stress exists.
    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. 6441-6443 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Relationships between the magnetic properties and the film structure of Mn/Al multilayers are examined by changing the thicknesses of Mn and Al layers. X-ray diffractions show that the Mn lattice spacing measured vertical to the substrate becomes smaller by increasing the Mn layer thickness or by decreasing the Al layer thickness. Saturation magnetization and magnetic anisotropy vary depending on the change of the Mn lattice spacing. Ferromagnetism and magnetic anisotropy of Mn/Al multilayers are closely related to the strain in the Mn lattice.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In a rigid disk a very smooth surface is desirable for high density recording, while it tends to stick to the magnetic head. To avoid this difficulty, the mechanical texturing (M/T) is widely used. Unfortunately very low flying height can't be achieved with the M/T. To improve the flying height, authors have developed a new texturing process using anodically oxidized aluminum substrates named chemical texturing (C/T).1 Aluminum anodic oxide films have a regularly arranged honeycomb structure and uniform and roughness-controlled surfaces were formed by etching process of chemical texturing. In the present research, the relation between the recording and tribological properties and the etching conditions were investigated. On C/T substrates Cr, a longitudinal magnetic layer CoNi, C were sputtered in an inline sputtering equipment. The surface of the sputtered layer was flat (Ra〈5 A(ring)) and uniform. Magnetic and electrical properties (coercive force, squareness, over write, modulation and so on) were examined. In spite of isotropy on the disk surfaces, the modulation caused by the inline sputtering was not observed, and high coercive force of 1200 Oe was obtained. Tribological properties (gride height, CSS, friction) were measured. Gride height was lower than 0.1 μm, and CSS more than 30 000 cycles. In semi-pilot plant production, thousands of C/T disks were prepared. Yield of disks having less than 5 missing and/or extra pulses was higher than 95%.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 570-578 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The physical properties (transition energy, oscillator strength, linewidth, binding energy, and reduced effective mass) of room temperature excitons in compressively strained InGaAs/InGaAlAs multiquantum-well (MQW) structures as a function of the well width have been investigated for the first time by both absorption measurements and photomodulated transmittance measurements. Photomodulated transmittance spectroscopy has been successfully applied to clearly reveal critical transition points. Measured transition energies are in good agreement with a model which includes the heavy hole and light hole splitting due to the strain. For well widths of 2.5–7.5 nm, oscillator strengths are smaller for the strained layer MQWs than for the lattice-matched MQWs by 35%–45%. This is due to the larger exciton radius for the strained MQWs resulting from smaller in-plane reduced effective masses (0.031–0.038m0), which are 65% of those of the lattice-matched MQWs.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 3633-3640 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electron transport was studied in AlGaAs/GaAs wires fabricated using focused Ga-ion-beam implantation. Single-wire samples 0.2–10 μm wide and 20 μm long were prepared with various ion doses ranging 2×1011–4×1012 cm−2; multiple-wire samples 0.1–0.3 μm wide and 10 μm long were prepared with an ion dose of 2×1011 cm−2. Electron mobility is reduced in the narrow wires because of the implantation-induced damage, and this mobility degradation is diminished by reducing the ion dose. These behaviors are consistently explained in terms of a diffusive scattering effect inside the channel and at the sidewall of the channel. Mobility in wires with the 2×1011 cm−2 ions is predominantly determined by the sidewall specularity. A 0.2-μm-wide wire with this ion dose exhibits a mobility of 2×105 cm2/(V s) and a specularity above 0.8. These values exceed those previously reported for wires fabricated using ion implantation and probably arise from the annealing employed in the present work. Conductance steps are observed with a single 0.2-μm-wide wire, and enhanced transconductance steps occur in multiple-wire samples. These behaviors are related to mobility modulation that occurs when one-dimensional subbands cross the Fermi level.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3022-3028 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The transport characteristics of in-plane-gated wires, in which the conducting two-dimensional electron gas (2DEG) channel and the 2DEG gates are separated by focused Ga-ion-beam scanned lines, are studied at low temperature (1.5 K). They are understood as a combination of the normal field-effect-transistor (FET) characteristics and a peculiar resistance jump at the channel pinch-off threshold. In the normal FET region, the depletion region spreading is gradually controlled by a gate voltage applied to the in-plane gates. The channel conductance variation by the gate voltage is explained by the change of the effective channel width rather than by the change of the carrier density. The variable range of the effective wire width is equal to or less than 0.6 μm in the experiments. In spite of this small controllable value, the channel can be pinched off up to W=10 μm with a gate leakage current of less than 1 nA. The pinch off of the wide wires always occurs together with a resistance jump at the threshold. These characteristics are explained by the drastic extension of the depletion region for the case that a small gate leakage occurs through the AlGaAs (Si) layer but not through the two-dimensional electron gas at the heterointerface. This resistance jump produces an interesting negative drain conductance (drain current/drain voltage) in the drain-voltage–drain-current characteristics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4465-4467 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Correlation between the structure and the magnetic properties of Mn-Al multilayered films prepared by vacuum evaporation have been investigated. Films on MgO(100) substrates with layer thicknesses of 100 A(ring) or more were found to have structures with flat layers and (100) orientation of α-Mn, while a film on a glass substrate and a film with a layer thickness of 50 A(ring) on a MgO(100) substrate were seen to have variations in layer thicknesses and no crystal orientation of α-Mn. Saturation magnetizations for the former two films are more than several times greater than those for the latter two films. From these properties, it is judged that stacking of α-Mn layers with (100) surfaces and Al layers is an important factor for the evolution of ferromagnetic properties in Mn-Al multilayered films.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A high precision atomic polarimeter system for the use in beam-foil spectroscopy experiments with a few keV/amu heavy-ion beams has been developed. The polarimeter measures the circular polarization of fluorescences from the beam ion in-flight after the beam–foil interaction. The present system has two identical such polarimeters in both sides of the beam axis to reduce the systematic errors such due to the fluctuations of beam current, background and so on. A successful use of an ultrathin carbon foil (1.5 μg/cm2), which was durable for several hours against a few hundred nA beam irradiation, enabled the beam–foil experiments with such low energy heavy-ion beams. A performance test of the polarimeter system was carried out in the tilted foil experiments with a 1.7 keV/amu 14N+ beam. The atomic polarization was observed for the transition 1s22s22p3p 1D→1s22s22p3p 1P, whose fluorescence wavelength is 399.5 nm, in the N+ ion (N II). The polarization was approximately −2% for the tilt angle of −40° and showed monotone increasing with increasing tilt angle up to +2% for +40°. The polarization at 0° was (0.002±0.25)%, which is highly consistent with the expected polarization of 0%. This result indicates the high reliability of the present polarimeter system. This is the first tilted-foil experiment at such low beam energy. The present experimental technique will be very useful for studies of the polarization mechanism of the beam–foil interaction. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 588-590 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Two-dimensional electron or hole gases (2DEG or 2DHG) are confined at the same interface in an undoped heterostructure by an electric field generated by a top gate. The combination of ion-implanted ohmic regions, an undoped heterostructure with superlattice barriers, and a metal gate is used to fabricate structures by a conventional process without self-alignment. High-quality 2DEG and 2DHG with a carrier density up to 8×1011 cm−2 are formed with a small gate leakage current. Switching between 2DEG and 2DHG at the same heterointerface is achieved by changing the sign of the gate voltage. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: CoCrPt/TiCr perpendicular recording media having independently optimized nucleation and growth conditions have been prepared by changing the argon pressure during sputter deposition of each film. A low argon pressure CoCrPt nucleation layer produces strong c-axis perpendicular orientation that can be maintained during continued CoCrPt deposition at high argon pressure. The two-layer media combines increased particle separation from high pressure growth and strong orientation to produce higher signal to noise ratio than either high pressure or low pressure single layer CoCrPt media. TiCr underlayers, despite poor orientation and a noncolumnar structure, improve CoCrPt c- axis perpendicular orientation. Low argon pressure during TiCr deposition maximizes CoCrPt orientation. A TiCr bilayer having a low pressure nucleation layer followed by a high pressure growth layer improves performance of the subsequent CoCrPt layer. A TiCr bilayer having a high pressure growth layer followed by a thin low pressure template produces even greater recording performance enhancement. This media has Hc=2560 Oe, D50=90 kfci and S0/Nd at 240 kfci=4.0. An identical CoCrPt layer deposited on the low pressure TiCr underlayer has Hc=1850 Oe, D50=80 kfci and S0/Nd at 240 kfci=2.4. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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