Open AccessComparisons between the generation and properties of rotational remanent magnetization and anhysteretic remanent magnetization
Author(s) -
Edwards J.
Publication year - 1980
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.1980.tb04862.x
Subject(s) - remanence , rotation (mathematics) , demagnetizing field , field (mathematics) , coercivity , magnetization , condensed matter physics , thermoremanent magnetization , magnetite , nuclear magnetic resonance , magnetic field , mineralogy , geology , physics , mathematics , geometry , quantum mechanics , pure mathematics , paleontology
Summary. Partial anhysteretic remanent magnetizations and partial rotational remanent magnetizations (RRM) have been induced in two specimens, one a rock and the other a synthesized cylinder of magnetite powder and plasticene. Partial anhysteretic remanent magnetizations have been found to conform to a known algebraic additive law, but partial RRMs do not appear to obey a corresponding law at the frequency of rotation chosen (0.21 cycle s ‐1 ). Other very clear differences between anhysteretic and rotational magnetizations have been observed. A relatively very large partial RRM may be induced by applying the rotation only while the alternating field is held at one particular peak value. Furthermore, when the peak field was increased by 10 mT (20 per cent) or more after stopping the rotation, very significant amounts of RRM, induced by the rotation, were found to have survived the subsequent increase of the alternating field, i.e. the magnetic ‘memory’ of an earlier rotation was not erased by the application of an alternating field whose peak value was higher than that at which the rotation was applied. By contrast, barely significant partial anhysteretic remanent magnetizations were observed after a steady field had been applied only while the alternating field was held at one particular peak value. Neither of the specimens was able to ‘memorize’ a steady field which had been applied earlier and removed before the peak value of the alternating field was increased further, and then decreased to zero. A procedure for demagnetizing a RRM was investigated. It was found that by applying sharp and regular reversals of rotation to the specimen during the decrease of the alternating field, a very much smaller net RRM was induced compared with the magnitude of the RRM induced when the alternating field was decreased to zero after the specimen had stopped rotating. These results imply that the interaction between rotational motion and an alternating field can align magnetizations whose coercive forces are significantly greater than the peak alternating field.