Premium
The Field‐Dependence of AC Susceptibility in Titanomagnetites: Implications for the Anisotropy of Magnetic Susceptibility
Author(s) -
De Wall Helga
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2000gl008515
Subject(s) - anisotropy , condensed matter physics , magnetic susceptibility , field dependence , curie temperature , field (mathematics) , magnetic field , materials science , ferromagnetism , physics , mathematics , quantum mechanics , pure mathematics
In a case study on titanomagnetite‐bearing rocks from the Riedheim dike of (Hegau volcanics, SW‐Germany), samples of varying composition (Curie temperatures of 128 to 440 °C) have been tested for their ac field‐dependence of low‐field susceptibility. The measurements were performed in ac fields of 30 and 300 A/m. In order to quantify the field‐dependency of titanomagnetites, the parameter χ Hd [%] = [(χ 300A/m ‐ χ 30A/m ) / χ 300A/m ] × 100 is introduced, which ranges from 4.1 to 26.5. A liear relationship has been determined between the Curie temperature of the titanomagnetites and the log χ Hd parameter. The anisotropy factor (P′) of the anisotropy of magnetic susceptibility (AMS) ellipsoid is significantly enhanced in the higher ac field, while the shape factor (T) appears to be insensitive to the field amplitude. However, despite these variations, the principal axes of the AMS‐ellipsoids remain unchanged in orientation.