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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic domain observations on magnetite and titanomaghemite grains (0.5–10 μm) (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: By using the Bitter method, we have observed the magnetic domain structures of natural titanomaghemite grains and magnetite crystals (0.5–10 μm) that were grown in a glass ceramic matrix. The observations were carried out in a range of applied magnetic fields and were correlated to the hysteresis properties of the bulk samples. Our observations show that simple, lamellar structures cannot explain the high-field hysteresis behaviour in either the titanomaghemite or the magnetite sample. This high-field behaviour is probably dominated by complicated, stress-influenced domain structures and rotation processes. A plot of the number of lamellar domains observed in magnetite grains versus their grain size yields a single-domain to two-domain transition size of 0.25 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06353.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Three-dimensional micromagnetic calculations for magnetite using FFT (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 124 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An unconstrained 3-D micromagnetic model for magnetite grains with resolutions up to 23 × 23 × 63 is presented. The model has been used to investigate the magnetic domain states of submicron parallelepipeds with various elongations. The method of fast Fourier transformation (FFT) has been implemented in three dimensions to accelerate the computation of the magnetostatic energy and its gradient, assuming constant magnetization for each subcube of the model. A 3-D implementation of the exchange energy and its gradient, using a five-point formula to approximate the Laplace operator, was chosen. Special attention has been paid to single-domain (SD) or flower states and pseudo-single-domain (PSD) configurations. A circular configuration, called vortex state, has been found to have the lowest energy of various PSD states. As a local energy minimum (LEM), the free energy of the vortex state is compared to that of a single-domain state. A comparison of these energies is used to determine a lower and an upper threshold size for the SD to PSD transition. In the interval between these two threshold sizes both configurations, SD and PSD, coexist. Above the upper threshold size we found metastable double-vortex configurations which seem to represent three-domain structures with closure domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06354.x
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    Paper (German National Licenses)
    Fulltext
  • 3
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    (Table 2) Age model control points, and CaCO3 and TOC accumulation rates of ODP Leg 167 sites (1997)
    PANGAEA
    In:  Supplement to: Ravelo, Ana Christina; Lyle, Mitchell W; Koizumi, Itaru; Caulet, Jean-Pierre; Fornaciari, Eliana; Hayashida, Akira; Heider, Franz; Hood, Julie A; Hovan, Steven A; Janecek, Thomas R; Janik, Aleksandra G; Stax, Rainer (1997): Pliocene carbonate accumulation along the California Margin. Paleoceanography, 12(6), 729-741, https://doi.org/10.1029/97PA02525
    Details
    Publication Date: 2024-01-09
    Description: Recent modeling studies call on increased ocean heat transport to explain high-latitude warming observed for intervals throughout the middle Pliocene. Possible vehicles for ocean heat transport are the poleward arms of the subtropical gyres. Sites from the California margin (Ocean Drilling Program Leg 167) provide monitors of wind field within the eastern arm of the gyre which may be an indication of basin-wide subtropical gyral strength. At most sites (water depths from 1106 to 4212 m) CaCO3 mass accumulation rate (MAR) was highest in the middle Pliocene (3.5-2.0 Ma). This high CaCO3 MAR 'event' is attributed primarily to higher CaCO3 production due to higher offshore upwelling associated with the zone of the greatest wind stress curl. Thus, in the middle Pliocene, there was enhanced wind stress curl along the California margin, and possibly enhanced North Pacific sub-tropical gyral circulation and meridional ocean heat advection.
    Keywords: 167-1010; 167-1011; 167-1012; 167-1013; 167-1014; 167-1016; 167-1017; 167-1018; 167-1019; 167-1020; 167-1021; Accumulation rate, calcium carbonate; Accumulation rate, total organic carbon; AGE; Age, maximum/old; Age model; Ageprofile Datum Description; Calcium carbonate; Carbon, organic, total; COMPCORE; Composite Core; Density, dry bulk; Depth, composite; Depth, composite bottom; Depth, composite top; DEPTH, sediment/rock; Elevation of event; Event label; Joides Resolution; Latitude of event; Leg167; Longitude of event; North Pacific Ocean; Nuttallides rugosa, δ13C; Ocean Drilling Program; ODP; Sedimentation rate
    Type: Dataset
    Format: text/tab-separated-values, 1353 data points
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    DATA PANGAEA
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