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Reciprocal and real space maps for EMCD experiments
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
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2010 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 110, no 11, 1380-1389 p.Article in journal (Refereed) Published
Abstract [en]

Electron magnetic chiral dichroism (EMCD) is an emerging tool for quantitative measurements of magnetic properties using the transmission electron microscope (TEM), with the possibility of nanometer resolution. The geometrical conditions, data treatment and electron gun settings are found to influence the EMCD signal. In this article, particular care is taken to obtain a reliable quantitative measurement of the ratio of orbital to spin magnetic moment using energy filtered diffraction patterns. For this purpose, we describe a method for data treatment, normalization and selection of mirror axis. The experimental results are supported by theoretical simulations based on dynamical diffraction and density functional theory. Special settings of the electron gun, so called telefocus mode, enable a higher intensity of the electron beam, as well as a reduction of the influence from artifacts on the signal. Using these settings, we demonstrate the principle of acquiring real space maps of the EMCD signal. This enables advanced characterization of magnetic materials with superior spatial resolution.

Place, publisher, year, edition, pages
2010. Vol. 110, no 11, 1380-1389 p.
Keyword [en]
EMCD, magnetic circular dichroism, electron energy-loss spectra, transmission electron microscopy
National Category
Physical Sciences Condensed Matter Physics Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-108011DOI: 10.1016/j.ultramic.2010.07.004ISI: 000282562100005OAI: oai:DiVA.org:uu-108011DiVA: diva2:233899
Available from: 2009-09-03 Created: 2009-09-03 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Transmission Electron Microscopy for Characterization of Structures, Interfaces and Magnetic Moments in Magnetic Thin Films and Multilayers
Open this publication in new window or tab >>Transmission Electron Microscopy for Characterization of Structures, Interfaces and Magnetic Moments in Magnetic Thin Films and Multilayers
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Structural characterization is essential for the understanding of the magnetic properties of thin films and multilayers. In this thesis, both crystalline and amorphous thin films and multilayers were analyzed utilizing transmission electron microscopy (TEM). High resolution TEM and electron diffraction studies emphasize on the growth of amorphous Fe91Zr9 and Co68Fe24Zr8 on both Al2O3 and Al70Zr30 in multilayer structures by magnetron sputtering. The properties of the growth surfaces were found to strongly influence the formation of nano-crystallites of the magnetic material at interfaces. Field induced uniaxial magnetic anisotropy was found to be possible to imprint into both fully amorphous and partially crystallized Co68Fe24Zr8 layers, yielding similar magnetic characteristics regardless of the structure. These findings are important for the understanding of both growth and magnetic properties of these amorphous thin films.

As magnetic systems become smaller, new analysis techniques need to be developed. One such important step was the realization of electron energy-loss magnetic circular dichroism (EMCD) in the TEM, where information about the ratio of the orbital to spin magnetic moment (mL/mS) of a sample can be obtained. EMCD makes use of angular dependent inelastic scattering, which is characterized using electron energy-loss spectroscopy. The work of this thesis contributes to the development of EMCD by performing quantitative measurements of the mL/mS ratio. Especially, methods for obtaining energy filtered diffraction patterns in the TEM together with analysis tools of the data were developed. It was found that plural inelastic scattering events modify the determination of the mL/mS ratio, wherefore a procedure to compensate for it was derived. Additionally, utilizing special settings of the electron gun it was shown that EMCD measurements becomes feasible on the nanometer level through real space maps of the EMCD signal.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 86 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 669
Keyword
Transmission electron microscopy, TEM, magnetism, multilayer, superlattice, thin films, amorphous metals, electron energy-loss magnetic circular dichroism, EMCD, electron diffraction
National Category
Condensed Matter Physics Condensed Matter Physics Physical Sciences
Research subject
Engineering Science with specialization in Solid State Physics; Physics of Matter
Identifiers
urn:nbn:se:uu:diva-107941 (URN)978-91-554-7599-4 (ISBN)
Public defence
2009-10-16, Polhemsalen, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2009-09-24 Created: 2009-09-01 Last updated: 2011-05-02Bibliographically approved

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Lidbaum, HansRusz, JánRubino, StefanoHjörvarsson, BjörgvinOppeneer, Peter M.Eriksson, OlleLeifer, Klaus

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