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  • 1990-1994  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Galvanomagnetic voltages in the vicinity of a domain wall in ferromagnetic thin films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1550-1555 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic Ni-Fe films of thickness 〈85 nm contain Néel or crosstie walls, with wall thickness as large as 6 μm. Because of the anisotropic magnetoresistance Δρ/ρ0(approximately-equal-to)2% in Ni-Fe, the electrical resistivity is slightly larger inside a wall than in the adjacent domains, for currents normal to the wall. This should result in a detectable increase dV of the ohmic voltage between two miniature potential probes when a wall is located between them. For reasonable values of the dc current density, our calculations predict dV(approximately-equal-to)9 μV per wall. When the current is parallel to Néel walls, there should be a local decrease of the resistivity inside each wall, manifested as a decrease of the average sample resistance. This effect seems to provide an explanation for the upward resistance jumps observed in Ni-Fe magnetoresistive reading heads when Néel walls disappear. Also, because of the planar Hall effect, a voltage V should appear between two potential probes when one probe is located at the wall center.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347248
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Current-induced displacements and precession of a Bloch wall in Ni-Fe thin films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6405-6407 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rectangular or exponential current pulses of duration (approximately-equal-to)0.1 μs traversing a Bloch wall are found to induce wall displacements Δx≤10 μm/pulse in a Ni81Fe19 film of thickness (approximately-equal-to)263 nm. The critical current density for wall displacement is jc(approximately-equal-to)1.35×106 A/cm2, about 20–200 times lower than for Néel or cross-tie walls investigated earlier. Wall motion arises probably from the precession of wall spins under the influence of the "s-d exchange torque'' exerted by conduction electrons crossing the wall. The low jc value and easy precession of spins in a Bloch wall reflect the very small value (approximately-equal-to)300 μT of the wall demagnetizing field which opposes spin orientation out of the wall plane in films of this thickness. A dc in-plane hard-axis field causes a linear decrease of jc. A dc easy-axis field smaller than Hc produces only a very slow decrease of jc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352611
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of galvanomagnetic voltages at a magnetic domain wall in Ni-Fe films : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5825-5827 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Ni81Fe19 film of 110 nm thickness is traversed by a dc current density normal to the easy axis. Two sharp tungsten wires serve as potential probes, distant by 210 μm along the easy axis. A charged wall, oriented at an angle to the easy axis, is made to creep slowly across the sample by applying dc easy axis and 60-Hz hard axis magnetic fields. The dc voltage between the probes is found to vary whenever the wall passes by the probes. The variation has the form of a voltage peak of (approximately-equal-to)40 μV typical height. These peaks are caused by the planar Hall effect, in combination with a canting of the domain magnetization near the charged wall. In the case of a current parallel to the easy axis and normal to the line joining the probes, a steplike voltage variation ≤150 μV is observed for an uncharged wall in the presence of a dc hard axis field. Planar Hall effect and (field induced) domain canting are again responsible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350123
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Theory of magnetoresistance in concentrated ferromagnetic alloys (invited) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5549-5554 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Existing values of the magnetoresistance (ρ(parallel)−ρ⊥)/ρ0 for crystalline Ni1−xFex, Ni1−xCox, Ni1−xMnx, Fe1−xCrx, and Fe1−x-Vx alloys depend on x in a way which disagrees with the traditional Smit theory, based on the Born approximation. The reasons are related to the variation of the 3d wave-function amplitude between chemically different atoms and, in turn, to a variation of s-d scattering intensity. Experimental atomic moments indicate that this 3d amplitude variation is large. The variation is related to the fact that d-d scattering is strong and resonant. We predict large deviations from Nordheim's rule ρ↓∝ x(1−x) where ρ↓ is the spin-down resistivity, similar to the deviations found experimentally. Correspondingly, (ρ(parallel)−ρ⊥)/ρ0 is much larger for x(approximately-equal-to)0 than for x(approximately-equal-to)1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345882
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  • 5
    Electronic Resource
    Electronic Resource
    Prediction of Shapiro steps in the dc voltage across a magnetic domain wall traversed by a dc current and exposed to high-frequency magnetic fields : 35th Annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4683-4685 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In metallic ferromagnets, a current of electrons traversing a domain wall exerts a torque on the wall spins through the s-d exchange interaction. This torque may induce a precession of the wall spins around the easy axis. In turn, the wall precession at a rate ω0 generates a dc voltage δV across the wall, given by the formula eδV = (h-dash-bar)ω0 similar to the Josephson equation for superconducting junctions. In the present theoretical work, a high-frequency (hf), in-plane, hard-axis magnetic field is also applied. For a certain range of values of the dc current density, the rate of wall precession is synchronous with that of the hf drive field. In other ranges, precession is asynchronous, or there is no precession. As a result, the voltage δV has a stepwise dependence on the current density. This is the analog of the well-known Shapiro steps for the superconducting Josephson voltage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348296
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Motion of a magnetic domain wall traversed by fast-rising current pulses (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 2721-2726 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Bloch wall is predicted to undergo finite displacements when traversed by a current pulse with short rise time ≤20 ns and long fall time, in thin films of metallic ferromagnets. In Ni–Fe films of thickness 85–150 nm, pulses with peak current density (approximately-equal-to)1×107 A/cm2 are expected to induce wall displacements of order 0.1–1 μm. This effect originates from the s-d exchange interaction. It is phenomenologically similar to the well-known "wall streaming'' motion of Bloch walls subjected to fast-rising pulses of hard-axis magnetic field. The effect is related to the existence of a novel, current-induced, term in the expression for the momentum of a magnetic domain wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351045
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  • 7
    Electronic Resource
    Electronic Resource
    Current-induced displacements of Bloch walls in Ni-Fe films of thickness 120–740 nm (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4787-4792 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rectangular current pulses of duration 0.14 μs, flowing across Bloch domain walls in Ni81Fe19 films, cause displacements Δx of these walls, observable by Kerr-contrast microscopy. In zero magnetic field, Δx reaches (approximately-equal-to)14 μm/pulse at current densities (approximately-equal-to)30% above the value jc where wall motion starts. This critical current density is jc(approximately-equal-to)1.2×1010 A/m2 for a film thickness w=263 nm. We have measured jc versus film thickness for w=120–740 nm, and find jc∝w−2.1. This suggests strongly that the observed wall motion is associated with an S-shaped distortion of the wall by the circumferential magnetic field of the current. This wall distortion is limited by the wall surface tension. The wall structure becomes that of the so-called asymmetric Néel wall. Through wall distortion, the current pulse pumps kinetic energy and momentum into the wall. This kinetic energy is then dissipated during ballistic wall motion happening largely after the end of the pulse. We also find jc to be independent of pulse duration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357250
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  • 8
    Electronic Resource
    Electronic Resource
    Electroabsorption and saturation behavior of InGaAsP/InP/InAlAs multiple superlattice electron transfer optical modulator structures (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1110-1112 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report substantial progress in the growth of multi-quantum-well electron transfer optical modulator structures by metalorganic vapor phase epitaxy, which is made possible as a consequence of the highly abrupt modulation doping of donors and acceptors in InP-reservoir and InAlAs-barrier layers, respectively. Due to a large thermionic emission barrier provided by the type II InP/InAlAs interface, the InGaAsP/InP/InAlAs devices exhibit extremely low leakage current densities. We observe distinct and sharp features related to absorption quenching in differential transmission spectroscopy. Moreover, the saturation intensities of electron transfer modulators are determined. The underlying physical mechanism is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109796
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  • 9
    Electronic Resource
    Electronic Resource
    Observation of a current-induced force on Bloch lines in Ni-Fe thin films (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5941-5943 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Finite displacements of Bloch lines, induced by current pulses directly traversing the sample, have been observed by the ferrofluid technique in Ni81Fe19 films of thickness 33–68 nm containing cross-tie domain walls. The pulses of duration ≤ 1 μs are normal to the wall. Bloch lines move along the wall whenever the current density exceeds a critical value ≈1×1012 A/m2. It is possible to partly control the sense of the central spin of Bloch lines by applying a field μ0H≈100 μT normal to the film during Bloch-line creation. The sense of the current-induced force on Bloch lines is found to depend on the sense of the central spin of Bloch lines, and agrees with the sense of the theoretically predicted s-d gyroscopic force which arises from s-d exchange. However, the average value of the force is about four times smaller than the predicted value for a one-band model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346110
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