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|Title: ||Effect of exchange and magnetostatic interactions on grain boundaries|
|Authors: ||Barron, Louise Lillias Margaret|
|Supervisor(s): ||Williams, Wyn|
|Issue Date: ||28-Jun-2011|
|Publisher: ||The University of Edinburgh|
|Abstract: ||Magnetic minerals are abundant within our Earth's crust and can retain, through
one of a number of processes, a remanent magnetisation induced by the Earth's
magnetic field. Analyses of palaeomagnetic samples have been used for the past
fifty years to improve our understanding of many of the Earth's major processes.
Recent studies utilising newly developed imaging techniques, namely holographic
transmission electron microscopy, have for the first time allowed direct
observations of the magnetic structure in palaeomagnetic samples on a nanoscale.
It is commonly observed that igneous rocks contain closely packed magnetic lamellae
with a non-magnetic matrix, a result of the chemical process of exsolution.
However, the results of current micromagnetic models, generated to predict the
magnetic structure within such samples, are not in agreement with these direct
observations. The results do, however, show strong similarities to the direct observations.
The discrepancies between the direct observations and micromagnetic
models indicate a lack of understanding of the magnetic interactions within such
samples. To examine this two distinct hypotheses have been tested.
Firstly, the geometry of the system has been altered to examine the effect of
this on the magnetic structure of the grains. Secondly, a multiphase model has
been produced. This multiphase model allows the simulation of more complicated
systems that include more than one magnetic material in direct contact. This
multiphase model has allowed us to examine the effect of varying the exchange
in these multiphase structures and its effect on the modelled magnetic structure.
Further, this multiphase model has allowed us to examine theoretical systems
involving combinations of magnetic materials commonly found in palaeomagnetic
|Sponsor(s): ||Natural Environment Research Council (NERC)|
|Keywords: ||micromagnetic modelling|
|Appears in Collections:||Earth and Planetary Science Research Institute thesis and dissertation collection|
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