Low-Field AMS at Increating Field Strenghts in Hematite Single Crystals: Influence of the Rayleigh Region on the Magnetic Fabric Paramteres
Abstract
Hematite is a very abundant mineral in natural samples. It is one of the most important carriers of remanent magnetization. However its anisotropy is not well understood partially due to its high coercivity and complex behaviour. In particular the variation of low-field susceptibility with increasing low-fields seems to be out of the Rayleigh region for the field of 300 A/m used in most commercial instruments. This makes the main assumption of reversibility of magnetization with applied field used in magnetic fabric analysis to fail. It has been carried out an intensive study of the low-field susceptibility and anisotropy of magnetic susceptibility (AMS) at increasing low-fields in the range of 2-450 A/m in a collection of hematite single crystals. Standard rock magnetic properties, X-ray diffraction and mass spectrometry have also been determined in order to control the parameters influencing the low-field susceptibility variations with field. The AMS principal directions, shape of the AMS ellipsoid and degree of anisotropy are parameters that can vary with different applied field. It has been found that there is no correlation between magnetic properties like coercivity or saturation magnetization and the range in which the Rayleigh approximation is valid. However, there seems to be a correlation with the crystallite size determined from X-ray diffraction, suggesting that the Rayleigh region in hematite crystals is related to the spatial orientation of the physical domains within the basal plane.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGP41A1027G
- Keywords:
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- 1518 GEOMAGNETISM AND PALEOMAGNETISM / Magnetic fabrics and anisotropy;
- 1519 GEOMAGNETISM AND PALEOMAGNETISM / Magnetic mineralogy and petrology;
- 1540 GEOMAGNETISM AND PALEOMAGNETISM / Rock and mineral magnetism