Record details

Title
    Low-field variation of magnetic susceptibility and its effect on the anisotropy of magnetic susceptibility of rocks
Statement of responsibility
    František Hrouda
Author
    Hrouda, František
Language
    anglicky
Source title - serial
    Geophysical journal international
Vol./nr.
    Vol. 150
Pages
    p. 715-723
Year
    2002
Notes
    10 obr., 6 tab., 24 bibl.
    il.
    Zkr. název ser.: Geophys. J. int.
Subject group
    anizotropie
    hematit
    magnetická susceptibilita
    magnetit
    magnetometr
    metoda monokrystalová
    minerály magnetické
    pyrrhotin
Geographical name
    Brazílie-Minas Gerais
    Itálie střední
Keyword
    Anisotropy
    Effect
    Low-field
    Magnetic
    Rocks
    Susceptibility
    Variation
Abstract (in english)
   The theory of the low-field anisotropy of magnetic susceptibility (AMS) assumes a linear relationship between magnetization and the magnetizing field. This assumption is precisely valid in diamagnetic and paramagnetic minerals by definition, while in ferrimagnetic and antiferromagnetic minerals this relationship is in general non-linear (represented by a hysteresis loop), being linear only with very weak fields in which the initial susceptibility is measured. Recently, it has been shown that, in using common measuring fields, the field-independent susceptibility is measured in magnetite, while in pyrrhotite, haematite and titanomagnetite it may often be outside the initial susceptibility range. The problem can be solved in three ways. The simplest way is using very weak measuring fields (less than 10 A m-1), but this can result in significant lowering of sensitivity and precision.
   The second way is to respect the non-linearity and measure the susceptibility in so many directions that contour diagram of directional susceptibilities can be presented instead of a susceptibility ellipsoid. The third way is to measure the AMS within the Rayleigh law range and calculate the initial directional susceptibilities from which the AMS can be correctly determined using linear theory
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    11. 10. 2007
Import date
    8. 8. 2012