ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • American Physical Society  (233)
  • American Institute of Physics (AIP)  (33)
  • American Association for the Advancement of Science (AAAS)
Collection
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Absolute magnetometry at nanometer transverse spatial resolution: Holography of thin cobalt films in a scanning transmission electron microscope (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7418-7424 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method for the absolute measurement of magnetization at nanometer spatial resolution in magnetic thin films has been developed. A biprism placed in the illumination system of a scanning transmission electron microscope allows the operation of two distinct holography modes. The absolute mode displays a linear change in phase difference for regions of constant magnetization and thickness and the slope determines the magnitude of magnetization. The differential mode displays a constant value of phase difference in these regions allowing a simple and straightforward determination of domain wall profiles. Micromagnetic structure extracted from identical areas of thin Co films is compared using the new holography modes, differential phase constrast Lorentz microscopy and conventional Fresnel Lorentz microscopy in the same instrument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356658
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Magnetic structures and interactions in Ho/Y, Ho/Lu, and Ho/Er superlattices (invited) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6274-6277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ho/Y and Ho/Er superlattices have been grown by molecular-beam epitaxy using a Balzers UMS 630 instrument. The superlattices were grown on a sapphire substrate with an Nb buffer and Y seed layer. X-ray-diffraction techniques were used to characterize the crystallographic structure and neutron-diffraction techniques to determine the magnetic structures. The results for the Ho/Y systems were consistent with long-range order being formed coherently through the whole superlattice. The moments in the Ho layers were aligned in the basal plane and most of the structures could be described by helical structures with a turn angle between holmium planes of ΨH and between nonmagnetic Y planes ΨY. ΨY is found to be largely independent of temperature or superlattice, while ΨH decreases with decreasing temperatures and at low temperatures takes a commensurate value, so as to take advantage of the basal plane anisotropy. The results for the Ho/Er superlattices differ because the Er has a magnetic moment and the anisotropy favors alignment along the c axis. Between the ordering temperature of bulk Ho and bulk Er, the results are similar to those of the Ho/Y superlattices. The ordering propagates through the Er layers but the Er moments are not ordered. At lower temperatures the Er moments order in a cycloidal (a/c) structure with the basal plane components having fairly long-range coherence with the Ho moments, but the c-axis components having no coherence from one Er layer to the next.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358303
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Magnetic excitations in Fe-doped Mn3Si (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3403-3405 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Inelastic scattering of neutrons has been used to study the magnetic excitations in Fe-doped Mn3Si at 7 K. Mn3Si is an incommensurate antiferromagnet with magnetic Bragg points of the form (h,k,l)±(δ,δ,δ) with δ=0.425. Its magnetic excitations are qualitatively similar to those of the γ-Mn alloys, or of the itinerant antiferromagnet, chromium. The addition of 5 at. % of iron causes the value of δ to change to 1/2, so that the material becomes a commensurate antiferromagnet, greatly simplifying the shape of the excitation spectrum. In addition the low Néel temperature (23 K) permits measurements to be extended to energies of several times kTN. Constant energy scans through a magnetic Bragg point are qualitatively consistent with the spin-wave dispersion relation forming a "cone'' around the magnetic Bragg point. Low-energy scans (1 meV≤ΔE≤4 meV) are centered on the Bragg point and flat-topped, while at higher energies (5 meV≤ΔE≤15 meV) the peak is clearly resolved as double. A fit using a damped-harmonic oscillator cross section suggests that the slope of the dispersion relation increases with energy, and that the excitations are highly damped.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338761
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Poloidal rotation effects on a simulated resistive kink mode (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 174-179 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Through the principal use of the reduced magnetohydrodynamic version of the finite aspect ratio code [L. A. Charlton et al., J. Comput. Phys. 86, 270 (1990)], an m/n=1/1 resistive kink mode was poloidally rotated with the accompanying rotational shear. It was observed that the growth rate of this unstable mode can either decrease or increase as the applied equilibrium rotation is increased to near poloidal sonic speeds. Shear in the poloidal rotation profile is stabilizing, but only if the destabilizing effects of bulk rotation can be overcome. Therefore, the mode's stability was sensitive to the location of the rotation's peak relative to the eigenmode's spatial extent. The destabilizing effects of bulk rotation are apparently a rotationally enhanced beta, and the stabilizing effects appear to be caused by exceeding a critical rotational shear spatially averaged over the eigenmode structure. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326062
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Theory of beat wave excitation in an inhomogeneous plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 36-47 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The theory of beat wave excitation in a slightly inhomogeneous plasma is presented. While the theory is general it applies directly to the experiments performed in Alaska by the ionospheric heating facilities HIPAS [High Power Auroral Simulation, Radio Sci. 25, 1269 (1990)] and HAARP [High Frequency Active Auroral Research Project, Geophys. Res. Lett. 25, 257 (1998)]. A ray tracing (WKB) formalism appropriate for computations is developed. The computational implementation of this formalism and extensive results will be presented in a follow up to this paper. Also the beat wave excitation of upper-hybrid waves is investigated analytically. The complicated trajectories of these waves in the plasma are described. When this beat wave reaches the plasma wave resonance it can, in the HIPAS–HAARP experiments, attain nonlinear amplitude. The electrostatic upper-hybrid waves are trapped around the density maximum of the ionosphere. This trapping is investigated in detail. Beat wave pumping of the trapped modes is possible using HAARP and HIPAS or with split beams from HAARP. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329149
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Detonation: A mechanism for the explosive release of energy in a plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1848-1852 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The explosive release of energy by a plasma is a common and striking occurrence. A novel explosive scenario is demonstrated in a simple system that becomes unstable to a line tied Rayleigh–Taylor–Parker instability. The system crosses the linear instability threshold in a narrow region. Initially the instability grows in the narrow region. Two nonlinear terms become important at low amplitude. One nonlinearity causes the mode to grow explosively and narrow into finger-like structures. The other nonlinearity broadens the mode into the linearly stable region. The explosive nonlinearity makes the linearly stable region metastable. The combination of the two nonlinearities causes the mode to progressively destabilize the metastable region. Since this process is reminiscent of the detonation of chemical explosives, it is called detonation. Without dissipation the kinetic energy released is proportional to (t0−t)−6.4. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871980
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The continuum of unstable magnetohydrodynamic modes in a simple magnetized atmosphere (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1259-1264 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spectrum of unstable perturbations of a simple magnetized atmosphere is studied. Magnetic field lines are straight, horizontal, and line tied to conducting walls at both ends. The temperature has horizontal variation across the field lines as well as vertical variation. The unstable spectrum close to marginal stability is found to be continuous from zero to a maximum growth rate. The structure of the unstable continuum modes is calculated in the dissipationless limit. The presence of singularities in the eigenfunction does not affect the growth rate significantly, nor does it lead to plasma heating. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872783
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Current sheet formation along three-dimensional magnetic separators (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2885-2897 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It was shown by Syrovatskii [Sov. Phys. JETP 33, 933 (1971)] that a perfectly conducting two-dimensional magnetic field stressed externally develops a current sheet at an X point. A generalization of this analysis shows that a generic three-dimensional magnetic field develops a closed ribbon of current along separators already existing in the field. A separator is a field line that begins and ends at different magnetic null points. A current ribbon will occur if there are two distinct separators beginning and ending at the same two nulls, thus forming a loop. The magnetic field containing the current ribbon is in force-free equilibrium. An expression is found for the net current induced in the ribbon, and the magnetic energy stored by it, in terms of the amount of external stress. An electric field parallel to the current will facilitate reconnection and will dissipate the current and release the stored energy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871627
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Field-aligned coordinates for nonlinear simulations of tokamak turbulence (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2687-2700 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Turbulence in tokamaks is characterized by long parallel wavelengths and short perpendicular wavelengths. A coordinate system for nonlinear fluid, gyrokinetic "Vlasov,'' or particle simulations is presented that exploits the elongated nature of the turbulence by resolving the minimum necessary simulation volume: a long thin twisting flux tube. It is very similar to the ballooning representation, although periodicity constraints can be incorporated in a manner that allows E×B nonlinearities to be evaluated efficiently with fast Fourier transforms (FFT's). If the parallel correlation length is very long, however, enforcing periodicity can introduce artificial correlations, so periodicity should not necessarily be enforced in the poloidal angle at θ=±π. This method is applied to high resolution three-dimensional simulations of toroidal ion temperature gradient (ITG) driven turbulence, which predict fluctuation spectra and ion heat transport similar to experimental measurements. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871232
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Nonlinear magnetohydrodynamic detonation: Part I (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3565-3580 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sudden release of magnetic free energy, as occurs in spectacular solar flare events, tokamak disruptions, and enigmatic magnetospheric substorms, has long defied any acceptable theoretical explanation. Usual attempts at explaining these explosive events invoke magnetic reconnection and/or ideal magnetohydrodynamic (MHD) instability. However, neither of these two mechanisms can explain the fast time scales without nonlinear destabilization. Recently, Cowley et al. [Phys. Plasmas 3, 1848 (1996)] have demonstrated a new mechanism for nonlinear explosive MHD destabilization of a line tied Rayleigh–Taylor model. In this paper, this picture is generalized to arbitrary magnetic field geometries. As an intermediate step, the ballooning equation in a general equilibrium is derived including the effects of magnetic field curvature, shear, and gravity. This equation determines the linear stability of the plasma configuration and the behavior of the plasma displacement along the magnetic field line. The nonlinear equation which determines the time and spatial dependence, transverse to the equilibrium magnetic field, of the plasma displacement is obtained in fifth order of the expansion. The equations show that explosive behavior is a natural and generic property of ballooning instabilities close to the linear stability boundary. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872252
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...