January 5th to 6th 2017
Magnetic Interactions 2017The school of Geosciences at the University of Edinburgh is proud to host the 2017 Magnetic Interactions meeting taking place on the 5th and 6th of January 2017 in the Old Library, Drummond Street. This meeting is intended for the Earth Science magnetic community in the UK, but we welcome anyone (other subjects, international, etc.) to attend.
Registration is by email (firstname.lastname@example.org) please include the following information
- Preferred salutation and full name
- Dietary requirements
- Presentation title (if applicable)
- Presentation abstract (max 2000 characters)
- Preference of either a poster or oral presentation
Note to speakers: oral presentations should be 15 minutes long with the guide set at (12 minutes plus 3) for questions and invited speakers with 5 minutes for questions minutes for questions
Location of the conference is in the Old Library Drummond street, full location details are
The Old Infirmary Building
1 Drummond Street
Edinburgh EH8 9TT
Trevor AlmeidaVisualising dynamic chemical reactions and magnetic behaviour of nano-scale magnetic materials using electron microscopy
In order to better understand chemical phase transformations or magnetic behaviour in naturally occurring or synthetic samples, it is often necessary to investigate the underlying processes on the nano-scale. Transmission electron microscopy (TEM) allows atomic spatial resolution imaging and the development of in situ TEM experiments over recent years has provided fundamental insight into a range of dynamic processes. Further, combining in situ TEM experiments with techniques like electron holography or differential phase contrast imaging allows for imaging of magnetisation in nanostructures whilst under the influence of external stimuli; e.g. controlled atmospheres, temperature, etc. In this context, several examples of the use of in situ TEM and magnetic imaging will be presented.
Hematite (α-Fe2O3) is a widely occurring magnetic mineral and dilute iron (III) chloride solution acts as a simple precursor via an intermediate phase of akaganeite (β-FeOOH). Further, α-Fe2O3 NPs can be partially reduced to synthesise magnetite (Fe3O4) NPs. β-FeOOH and α-Fe2O3 reaction products are heated in situ within a TEM, under vacuum and hydrogen atmosphere, providing fundamental insight into the localised growth mechanism of α-Fe2O3 NPs, and their thermal reduction to Fe3O4, respectively.
Fe3O4 is the most magnetic naturally occurring mineral on Earth, carrying the dominant magnetic signature in rocks and providing a critical tool in palaeomagnetism. The oxidation of Fe3O4 to maghemite (γ-Fe2O3) is of particular interest as it influences the preservation of remanence of the Earth's magnetic field by Fe3O4. Further, the thermomagnetic behaviour of Fe3O4 grains directly affects the reliability of the magnetic signal recorded by rocks. Through combining electron holography with environmental TEM and in situ heating, the effects of oxidation and temperature on the magnetic behaviour of vortex-state Fe3O4 NPs are visualised successfully, for the first time.
Equiatomic iron-rhodium (FeRh) has attracted much interest due to its magnetostructural transition from its antiferromagnetic (AF) to ferromagnetic (FM) phase and is considered desirable for potential application in a new generation of novel nanomagnetic or spintronic devices. Several scanning TEM techniques are performed to visualise the localised chemical, structural and magnetic properties of a series of FeRh films.
Trevor P. Almeida, Adrian R. Muxworthy, Wyn Williams, Rafal E. Dunin-Borkowski, Takeshi Kasama, Thomas Hansen, András Kovács, Paul D. Brown, Rowan Temple, Jamie Massey, Christopher Marrows, Stephen McVitie
Jay ShahDusty olivine: our oldest record of rock magnetism?
The magnetic fields present during the early Solar System are crucial to understand and accurately model the accretionary dynamics of the Solar Nebula. Dusty olivine in the chondrules of unequilibrated chondrites remains unaltered since its formation in the first two to three million years of the Solar System, making it an ideal target for estimation of the magnetic field during this period of time. However, it is uncertain whether a magnetic record can be retained by these grains over four billion years without relaxing. Here we show that the magnetization of the iron in dusty olivine is stable for timescales far greater than that of our Solar System. Through in-situ thermal off-axis electron holography and micromagnetic simulation, we present the short-term observed and long-term modelled stability of dusty olivine iron. Our results demonstrate that the magnetization carried by dusty olivine is likely to be representative of the field present at the time of chondrule formation. Both experimental and computational findings are similar to those recently found for terrestrial magnetite, and in turn suggest more than ever that accurate ancient magnetic field estimates are possible from primitive extra-terrestrial materials.
J. Shah, A.R. Muxworthy, T.P. Almeida, A. Kovács, S.S. Russell, M.J. Genge, R.E. Dunin-Borkowski
Lennart de GrootMicromagnetic Tomography - first steps towards analyzing a volcanic sample
Methods to derive paleodirections or paleointensities from rocks currently rely on measurements of bulk samples (typically ~10 cc). The process of recording and storing magnetizations as function of temperature, however, differs for grains of various sizes and chemical compositions. Most rocks, by their mere nature, consist of assemblages of grains varying in size, shape, and chemistry. When dealing with lavas, this differing magnetic behavior often hampers paleointensity experiments; while occasionally a reliable paleodirection is obscured. If we would be able to isolate the contribution of each magnetic grain in a sample to the bulk magnetic moment of that sample, a wealth of opportunities for highly detailed magnetic analysis would be opened, possibly leading to an entirely new approach in retrieving paleomagnetic signals from complex mineralogies. Here we take the first practical steps towards this goal by developing a new technique: 'micromagnetic tomography'
Firstly, the distribution and volume of the remanence carrying grains in the sample must be assessed; this is done using a MicroCT scanner capable of detecting grains >1 micron. Secondly, the magnetic stray field perpendicular to the surface of a thin sample is measured using a high-resolution DC SQUID microscope. A mathematical inversion of these measurements yields the isolated direction and magnitude of the magnetic moment of individual grains in the sample. As the measured strength of the magnetic field decreases with the third power as function of distance to the exerting grain (as a result of decay in three dimensions), grains in the top 30-40 microns of our synthetic sample with a relatively low dispersion of grains in a matrix can be assessed reliably. We will discuss the potential of our new inversion scheme, and current challenges we need to overcome for both the scanning SQUID and MicroCT techniques before we can analyse 'real' volcanic samples with our technique.
Lennart de Groot, Annemarieke Báguin, Karl Fabian, Pim Reith, Ankur Rastogi, Auke Barnhoorn, Hans Hilgenkamp
Barbara A Maher
Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge and strongly magnetic behaviour. Previous work has shown a correlation between the amount of brain magnetite and the incidence of Alzheimer's disease (AD), and magnetite nanoparticles directly associated with AD plaques. We used magnetometry, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS) and energy dispersive x ray analysis (EDX) to examine the mineralogy, morphology, and composition of magnetic nanoparticles in and from the frontal cortex of 37 human brain samples, from subjects who lived in Mexico City and in Manchester, U.K.. These analyses identified the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting therefore an external, not internal, source. These brain magnetites, often found with other transition metal nanoparticles, display rounded morphologies and fused surface textures, reflecting condensation from an initially heated, iron-bearing source material. Such high-temperature magnetite 'nanospheres' are ubiquitous and abundant in airborne particulate matter (PM) pollution.
Because of their combination of ultrafine size, specific brain toxicity, and ubiquity within airborne PM, pollution-derived magnetite nanoparticles might be a possible AD risk factor. In addition to occupational settings (including, for example, exposure to printer toner powders), higher concentrations of magnetite pollution nanoparticles may arise in the indoor environment from open fires or poorly-sealed stoves used for cooking and/or heating, and in the outdoor environment from vehicle (especially diesel) and/or industrial PM sources.
Barbara A Maher