Open AccessA Phenomenological Model of Orientational Magnetic Anisotropy of Sediments
Author(s) -
Kosterov Andrei A.,
Shashkanov Vladimir A.
Publication year - 1996
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1996.tb06542.x
Subject(s) - anisotropy , remanence , condensed matter physics , geology , magnetization , magnetic anisotropy , field (mathematics) , phenomenological model , magnetic field , sedimentation , geophysics , physics , optics , sediment , mathematics , paleontology , quantum mechanics , pure mathematics
SUMMARY A phenomenological model has been proposed to investigate a magnetic anisotropy induced in sediments by a magnetic field applied during sedimentation. It is assumed that the aligning effect of the sedimentation field produces a Fisher distribution of grain magnetic moments. Thus, anhysteretic remanence (ARM) acquisition and ARM anisotropy were investigated for assemblages of identical grains with known intrinsic (micro) anisotropy. We have considered uniaxial grains, grains with two and three mutually orthogonal axes of easiest magnetization, and grains with four easiest axes directed along spatial diagonals of a cube. We have derived explicit formulae for the intensity and direction of anhysteretic remanence as a function of alignment degree and the orientation of the anhysteretic magnetization field with respect to the sedimentation field. Computation shows that for weakly aligned magnetic moments the ARM anisotropy of an assemblage of uniaxial grains is ellipsoidal, while for multiaxial grains under the same conditions it can be ignored. For assemblages with highly aligned grains, the ARM anisotropy is dependent on the intrinsic anisotropy of the grains.