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The interplay between exsolution microstructures and magnetic properties of fe bearing oxide minerals

Objective



Research objectives and content
The two most important magnetic minerals in nature are the
magnetite-ulvvspinel and ilmenite-hematite solid solutions. Both of these systems display characteristic microstructures associated with the process of subsolvus exsolution. These microstructures consist of fine-scale intergrowths of an Fe-rich ferrimagnetic phase within an Fe-poor paramagnetic matrix, and are responsible for the unusually high strength and stability of the natural remnant magnetization recorded by these minerals. The aim of this project is to investigate and understand the behaviour of several natural and synthetic magnetic minerals, which have previously been shown to display unusual magnetic properties related to the presence of fine-scale microstructures. The nature of the magnetic interactions in these minerals will be investigated using measurements of magnetic hysteresis loops in fields up to 12 T and at temperatures from 4 K to 1000 K, and measurements of magnetic susceptibility from room temperature to 973 K. The structural and chemical nature of the microstructures will be investigated using a combination of transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (XEDS), electron energy loss spectroscopy (EELS), and energy filtered imaging (EFI). These state-of-the-art techniques allow quantitative chemical information to be extracted with a spatial resolution approaching 50 AA, and qualitative elemental distributions to be determined with a spatial resolution approaching 5 AA.
Training content (objective, benefit and expected impact)
The main training aspect of this project involves learning to set-up and use the Gatan Imaging Filter (GlF), which is required for both EELS and EFI. The benefit of these techniques is that is they allows us to obtain chemical information about the sample with a high spatial resolution. This project is one of the first to apply these new techniques to a well defined mineralogical problem. We expect that results will have a large impact in the fields of mineralogy and palaeomagnetism by demonstrating the potential of these techniques in quantifying fine-scale microstructures in minerals. Links with industry / industrial relevance (22)

Coordinator

WESTFAELISCHE WILHELMS - UNIVERSITAET MUENSTER
Address
Corrensstrasse 24
D-48149 Münster