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Institut de minéralogie, de physique des matériaux et de cosmochimie

Magnetic nanoparticles

  • Biogenic nanoparticles

We study extracellular biogenic magnetite (Fe3O4) and magnetosomes of magnetotactic bacteria in order to compare them to chemically-synthesized abiotic magnetite. We use the Fe2+/Fe3+ ratio, which has a strong influence on magnetic anisotropy, as a criteria for measuring biogenicity*****.

  • Inverse thermoremanent magnetization

Some iron oxydes present in natural rocks (hemo-ilmenite and titanomagnetite) can acquire a thermoremanent magnetization in a reverse direction with respect to the Earth’s magnetic field.  Some iron oxides that are present in natural rocks (hemo-ilmenites and some  titanomagnetites) can acquire a thermoremanent magnetization that is oppositely oriented with respect to the magnetic field in which the rocks were formed. This has major consequences for the fidelity of the paleomagnetic recording and their applications in geomagnetism and plate tectonics. We have been looking for an explanation at the atomic level for this phenomenon.

  • Magnetic properties of cronstedtite and oxygen fugacity in the solar nebula.

Cronstedtite, {Fe2+, Fe3+}3[Si, Fe3+]2O5(OH)4, is a hydrated phyllosilicate present in carbonated chondrites (primitive meteorites) that is very rich in iron. Cronstedtite suggests an alteration episode involving its aquaeous phase early in the formation of solar system, under conditions of temperature and oxygen fugacity that are not well-known. The Fe2+/Fe3+ ratio that magnetic mineralogy methods can determine appears to be a key parameter in the determination of the conditions that were present at the formation of solar system.

  • Sediment magnetism

Magnetic measurements carried out on marine and continental sediments allow the acquisition of continuous sequences of paleomagnetic field variations and paleoclimatic and paleoenvironmental variations. We seek to quantify the impact of alteration of magnetic minerals on their ability to record the geomagnetic field or the climate variations.  

Experimental methods : HR-TEM, EELS, XAS, XMCD, FORC,
Theoretical methods : DFT, LFM.


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