Haematite natural crystals: non-linear initial susceptibility at low temperature



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Guerrero Suárez, Sara and Martín Hernández, Fátima (2016) Haematite natural crystals: non-linear initial susceptibility at low temperature. Geophysical journal international, 205 (3). pp. 1886-1889. ISSN 0956-540X

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Official URL: http://dx.doi.org/10.1093/gji/ggw134


Several works have reported that haematite has non-linear initial susceptibility at room temperature, like pyrrhotite or titanomagnetite, but there is no explanation for the observed behaviours yet. This study sets out to determine which physical property (grain size, foreign cations content and domain walls displacements) controls the initial susceptibility. The performed measurements include microprobe analysis to determine magnetic phases different to haematite; initial susceptibility (300 K); hysteresis loops, SIRM and backfield curves at 77 and 300 K to calculate magnetic parameters and minor loops at 77 K, to analyse initial susceptibility and magnetization behaviours below Morin transition. The magnetic moment study at low temperature is completed with measurements of zero field cooled-field cooled and AC susceptibility in a range from 5 to 300 K. The minor loops show that the non-linearity of initial susceptibility is closely related to Barkhausen jumps. Because of initial magnetic susceptibility is controlled by domain structure it is difficult to establish a mathematical model to separate magnetic subfabrics in haematite-bearing rocks.

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© The Authors 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society.
This work is supported by Project no CGL2011-24790 from Spanish Ministry of Economy and Competitiveness and Visiting Research Fellowships of Institute for Rock Magnetism (IRM, University of Minnesota, USA) to SGS. We thank to Dr. Dario Bilardello and Prof. Mike Jackson from IRM for fruitful suggestions and technical assistance during the stay of SGS in the IRM. To Dr. Dekkers who kindly provided the hematite grain-sizes fractions. The manuscript has benefited from comments of two anonymous reviewers and we also acknowledge comments and suggestiosn of editor Proffesor A. Biggin.

Uncontrolled Keywords:High-field experiments; Magnetic-susceptibility; Grain-size; Weak ferromagnetism; Morin transition; Anisotropy; Dependence; Pyrrhotite; Behavior; Rocks
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Geophysics
Sciences > Physics > Meteorology
ID Code:38622
Deposited On:22 Jul 2016 14:05
Last Modified:04 Aug 2016 08:40

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