2 edition of Analysis of the Remanence Coercivity Spectrum by Continuous and Alternating Fields found in the catalog.
Analysis of the Remanence Coercivity Spectrum by Continuous and Alternating Fields
Geological Survey of Canada.
|Series||Geological Survey of Canada Bulletin -- 372|
Therefore, approximately 10 per cent of this remanence is apparently carried by haematite and/or goethite. Two parameters are used to further identify the magnetic mineralogy: the remanent acquisition coercive force (B′ cr) (Dankers ) and the coercivity of remanence (B cr). These are the applied magnetic fields at which 50 per cent of the Cited by: A small loss of remanence continues below T V but the cooling curves level out below 80 K. In the warming half-cycle from 10 K, the remanence is almost unchanging until – K and then recovers a small amount—the so-called memory—in passing from the monoclinic to the cubic phase at T the 14 µm sample, there is a small dip and recovery of remanence around K, close to T V Cited by: 3.
Stirring between subsequent runs was extensively used in the analysis of the thermomagnetic behaviour of haematite and goethite as a function of grain size (i.e. coercivity) in various non-saturating magnetic fields (10– mT). Samples were then demagnetized in alternating fields (AF) up to mT, and an isothermal remanent magnetization (IRM) was imparted from 0 to T also using the MicroMag AGM. Subsequently the IRM at T was demagnetized in a stepwise backfield from 0 to − T to obtain coercivity of remanence (B cr).Cited by:
The magnetomineralogical interpretation of the Tinau-N section was based on a coercivity spectrum analysis of the IRM data, newly acquired for a few specimens, following the log-normal Gaussian decomposition technique, to discriminate the contribution of magnetic mineral phases with differing coercivity spectra, as outlined by Kruiver et by: 3. The Tibetan Plateau exerts a major influence on Asian climate, but its long-term environmental history remains largely unknown. We present a detailed record of vegetation and climate changes over the past million years in a lake sediment core from the Zoige Basin, eastern Tibetan Plateau. Results show three intervals with different orbital- and millennial-scale features superimposed on a.
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The analysis of the remanence coercivity spectrum by continuous and alternating fields: relationship between coercivity and alternating fields stability spectra. (not yet rated) 0 with reviews - Be the first. Paleomagnetism. Rocks -- Magnetic properties -- Measurement.
Remanent coercivity spectra have been determined for four dispersions of magnetite with mean particle sizes of – μm using four different methods: (1) acquisition of isothermal remanent magnetization (IRM) in continuous fields; (2) stepwise reversal of saturation IRM by opposite-polarity continuous fields; (3) stepwise alternating-field (AF) demagnetization of saturation IRM; Cited by: A higher coercivity component, probably hematite, is also sometimes present.
Interpretation and discussion The A component is probably a recently ac- quired secondary magnetization because of its low coercivity and low unblocking temperatures, combined with its post-tectonic age and similarity to the present Earth's magnetic field by: ARM is that remanence acquired when a sample is subjected to a decreasing alternating magnetic field in the presence of a small steady magnetic field (see Table ).
The alternating field must initially be of sufficient strength to be able to saturate the magnetic grains in the sample. The remanence coercivity of maghemite (and magnetite) is 1 to 2 orders of magnitude less than that of hematite.
The maghemite-to-hematite transition at about °C will be accompanied by a change in remanence coercivity. The measurements of H cr can be carried out after each heating step with an alternating force gradient magnetometer (μMAG) but the measurement procedure is considerably.
Reliability of paleointensity methods using alternating field demagnetization and anhysteretic remanence. Using natural volcanic rocks which acquired thermoremanence (TRM) in known fields, reliability of various palaeointensity methods using alternating field (AF Author: Masaru Kono. Changes in remanence, coercivity and domain state at low temperature in magnetite Oº zden Oº zdemira;*, David J.
Dunlopa, Bruce M. Moskowitzb a Department of Physics, University of Toronto at Mississauga, Mississauga, ON, Canada L5L 1C6 b Institute for Rock Magnetism, University of Minnesota, Minneapolis, MNUSA Received 17 July ; received in revised form 18 October.
The samples were crushed to a fine sand grain size and the k–T was measured at each 3 °C interval. The coercivity spectrum analysis (Dunlop, ) was performed by placing a specimen in a steady magnetic field that was progressively increased.
Chemical remanent magnetization is produced by an increase in grain volume at temperatures below the blocking temperature of the grain. The process is analogous to TRM acquisition but in the case of CRM the relaxation time [see Eq.
Remanence and Coercivity Remnance (or remanence or residual magnetism also residual magnetization) Sometimes the term retentivity is used for remanence. Remanence and Coercivity Remanence or remanent magnetization is the magnetization left behind in a ferromagnetic material (such as iron) after an external magnetic field is removed.
Both processes affect the fidelity of the sediments as a recorder of the ancient field direction and relative paleointensity. In the present study, we report a rock magnetic study of three sedimentary cores of the late Pleistocene Lisan formation from Lake Kinneret (Sea of Cited by: N2 - This work reports on advanced remanence and coercivity measurements undertaken on a set of perpendicular exchange-coupled composite (ECC) media, where the demagnetizing field, H-D, has been properly accounted for.
We find that, on correction, the shape of the hysteresis loop, and hence the shape of the remanence curve, changes significantly. The coercive force spectrum of magnetite at high temperatures: Evidence for thermal activation below the blocking temperature. Thermal activation of magnetization is the mechanism proposed by Néel to explain TRM (thermoremanent magnetization) and VRM (viscous remanent magnetization).
A cautionary tale for palaeomagnetists: A spurious apparent single component remanence due to overlap of blocking-temperature spectra of two components.
Induced Magnetization of Magnetite-titanomagnetite in Alternating Fields Ranging from A/m to 80, A/m; Low-field Susceptibility ( – A/m) and Beyond skew the coercivity spectrum. Purchase Methods in Palaeomagnetism - 1st Edition. Print Book & E-Book. ISBNBook Edition: 1.
Characterization of individual rock magnetic components by analysis of remanence curves. Fundamental properties of coercivity distributions. Introduction  In environmental magnetism and paleomagnetism, measuring magnetic hysteresis has become a routine process in characterizing remanence carriers of rocks.
In general, values of M s (saturation magnetization), M r (saturation remanence), and B c (coercivity) are determined from hysteresis loops after appropriate nonferrimagnetic slope by: A first sample set (set A) was collected to provide continuous data for a 3 m stratigraphic interval from S8 through the slightly weathered L8 up to S7.
All samples from set A were stepwise thermally demagnetized. Another independent sample set (set Y, collected about 1 m away from set A) was treated using alternating fields (AF) by: To test the ability of the magnetic‐core demagnetizer to discriminate multicomponent remanence, we applied strong fields of, and mT in sequence along, approximately, the X, ‐Y, and Z core axes to produce three components of roughly orthogonal isothermal remanent magnetization (IRM).
This sample is from the recrystallized, central lithoidal zone of the same welded ignimbrite Cited by: 1. Another kind of laboratory remanence is anhysteretic remanence or anhysteretic remanent magnetization (ARM). This is induced by exposing a magnet to a large alternating field plus a small DC bias field.As described above, progressive demagnetization is the standard procedure for determining the component content of the NRM.
Thermal and alternating field demagnetization characteristics indicate the blocking temperature and coercivity spectra, respectively, of the NRM components. A detailed record of variations in the direction and intensity of the geomagnetic field over the past Myrs has been obtained from an ∼‐m‐thick sedimentary section cored at ODP Site on the Feni Drift (North Atlantic).
The record has high resolution due to high mean sedimentation rates ( cm/kyr for the Brunhes Chron and cm/kyr for the Matuyama Chron), paleomagnetic Cited by: