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Article Dans Une Revue Geophysical Research Letters Année : 2010

Self-reversal of magnetization in oceanic submarine basalts studied with XMCD

Résumé

In oceanic basalts, self-reversal of magnetization can be produced during extreme low-temperature oxidation of titanomagnetite by ionic reordering, which leads to Néel 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.

Dates et versions

hal-00492891 , version 1 (17-06-2010)

Identifiants

Citer

C. Carvallo, P. Sainctavit, M.-A. Arrio, Y. Guyodo, R. L. Penn, et al.. Self-reversal of magnetization in oceanic submarine basalts studied with XMCD. Geophysical Research Letters, 2010, 37, pp.11306. ⟨10.1029/2010GL043390⟩. ⟨hal-00492891⟩
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