Remanent Magnetisation in Hemo-Ilmenite

نویسندگان

  • Morten Sales
  • Niels Bohr
چکیده

The natural remanent magnetisation of a crystal of South Norwegian hemoilmenite rock has been studied using neutron scattering to obtain knowledge on the sample’s origin-deposit’s contribution to magnetic anomalies of the Earth’s magnetic field. The sample consists of an ilmenite host (paramagnetic) with exsolution lamellae of hematite (canted antiferromagnetic), thereby having a large area of contact layer between the bulk and the lamellae, which have an average size of around 2 μm. The natural remanent magnetisation has been hypothesised to be caused by lamellar magnetism in the contact layers, and using polarised neutron diffraction we have measured the average angle by which the spins in the sample align with an external magnetic field. A close-to-90◦ angle would suggest canted antiferromagnetic moments to be the origin of the remanent magnetisation, whereas an angle of 0◦ would imply that the explanation is to be found in lamellar magnetism. Our results show an angle of ∼61◦, which suggests that a combination of both or more explanations are needed. Further investigations of the sample include the Néel transition, where the transition temperature was found to be ∼41.3 K. The critical exponent, β, was found to be 0.22, which suggest that the system cannot be modelled using only either a 3D Heisenberg or an Ising model.

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تاریخ انتشار 2014