Carvallo, C.; Sainctavit, P.; Arrio, M. A.; Guyodo, Y.; Penn, R. L.; Forsberg, B.; Rogalev, A.; Wilhelm, F.; Smekhova, A. (2010): Self-reversal of magnetization in oceanic submarine basalts studied with XMCD. American Geophysical Union, Washington, DC, United States, Geophysical Research Letters, 37 (11), georefid:2011-071274
Abstract:
In oceanic basalts, self-reversal of magnetization can be produced during extreme low-temperature oxidation of titanomagnetite by ionic reordering, which leads to Neel N-type magnetism. Titanomaghemites showing N-type reversal below room temperature were found in submarine basalts recovered during Ocean Drilling Program (ODP) Leg 197. In order to better understand the mechanism of self-reversal, we carried out X-ray magnetic circular dichroism (XMCD) at Fe K-edge at room temperature and low-temperature on such a titanomaghemite sample as well as on pure magnetite and maghemite samples. We found that the XMCD spectrum of the N-type titanomaghemite at 20 K is a mirror image of the XMCD spectrum at 300 K, which shows that the octahedral and tetrahedral subnetworks reverse in this process. Ligand-field multiplet calculations of XMCD at Fe K-edge help identify the contributions of the different elements in the measured XMCD spectra. This mechanism could also cause self-reversal above room temperature, which has important consequences for the reliability of paleomagnetic measurements.
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West: 172.0900 East: 172.0900 North: 34.5600 South: 34.5600
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