Open AccessThe rapid determination of rotational remanent magnetization and the effective field which produces it
Author(s) -
Stephenson A.,
Molyneux L.
Publication year - 1987
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1987.tb00735.x
Subject(s) - remanence , magnetite , shields , magnetization , field (mathematics) , rotation (mathematics) , magnetic field , demagnetizing field , natural remanent magnetization , nuclear magnetic resonance , condensed matter physics , physics , mineralogy , materials science , geology , composite material , electromagnetic shielding , mathematics , geometry , metallurgy , quantum mechanics , pure mathematics
Summary A new piece of equipment which enables the rapid determination of rotational remanent magnetization (RRM) to be made in strong alternating fields (up to 100 mT peak at 50 Hz) at high rotation speeds (1.9 times the AF frequency) is described. Simultaneous determination of the rotational anhysteretic remanent magnetization (ARM) acquired in a known weak direct field is also carried out. This enables an effective field ( B g ), which can be considered to produce RRM, to be found. B g (obtained at about 95 rev s −1 in an AF of peak value 80 mT) has been related to magnetite particle size (Potter & Stephenson 1986) and decreases from about 100 μT as the particle size of magnetite increases from ∼1 μm. The equipment is thus potentially useful for estimating average sizes of magnetite particles in rock samples and is designed to operate in such a way that cancellation of the local earth's field by mu‐metal shields or Helmholtz coils is not necessary.