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Morphology of amorphous Fe91Zr9/Al2O3 multilayers: Dewetting and crystallization
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of 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.
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 21, 214202-1-214202-6 p.Article in journal (Refereed) Published
Abstract [en]

Amorphous Fe91Zr9/Al2O3 multilayers grown by magnetron sputtering have been studied using x-ray reflectometry, x-ray diffraction, Rutherford backscattering spectrometry, and transmission electron microscopy. It could be demonstrated that on the interface between the Fe91Zr9 and the Al2O3, crystalline grains are formed, that for very small repetition thicknesses destroy the periodicity of the multilayers by accumulative roughness. Understanding these effects would enable substantial improvement of the quality of nanolaminated amorphous layers.

Place, publisher, year, edition, pages
2007. Vol. 75, no 21, 214202-1-214202-6 p.
Keyword [en]
Intermetallic compounds, Amorphous semiconductors, metallic glasses, glasses, X-ray reflectometry, Transmission electron microscopy
National Category
Physical Sciences Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-11395DOI: 10.1103/PhysRevB.75.214202ISI: 000247624700041OAI: oai:DiVA.org:uu-11395DiVA: diva2:39164
Available from: 2007-09-11 Created: 2007-09-11 Last updated: 2017-12-11Bibliographically 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
2. Amorphous, Nanocrystalline, Single Crystalline: Morphology of Magnetic Thin Films and Multilayers
Open this publication in new window or tab >>Amorphous, Nanocrystalline, Single Crystalline: Morphology of Magnetic Thin Films and Multilayers
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Properties of magnetic thin film devices cannot be understood without detailed knowledge of their structure. For this purpose, a variety of thin film and multilayer systems have been studied. Both reciprocal space (low energy electron diffraction, reflection high energy electron diffraction, X-ray diffraction and reflectometry) and direct space (transmission electron microscopy) as well as Rutherford backscattering spectrometry have been applied.

To gain understanding of an oxidation procedure for the growth of magnetite layers, thermal stability of iron layers on molybdenum seed layers has been investigated.

Following the mosaicity and the out-of-plane coherence length over different ratios between the constituting layers allowed a deeper understanding of the limits of metallic superlattices. This, together with an approach to use hydrogen in the process gas during magnetron sputter epitaxy, opens routes for the growth of metallic superlattices of superior quality.

A non-isostructural multilayer/superlattice system, Fe/MgO, has been investigated. In turn, this gave more understanding how superlattice diffraction patterns are suppressed by strain fields.

As an alternative route to single-crystalline superlattices, amorphous multilayers present interesting opportunities. In this context, crystallization effects of iron/zirconium layers on alumiunium oxide were studied. Understanding these effects enables significant improvement in the quality of amorphous multilayers, and allows avoiding these, growing truly amorphous layers.

Both the substantial improvement in quality of metallic superlattices, approaching true single-crystallinity, as well as the improvements in the growth of amorphous multilayers give rise to opportunities in the field of magnetic coupling and superconducting spin valves.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 77 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 378
Keyword
Physics, Multilayer, Superlattice, X-ray diffraction, X-ray reflectometry, electron diffraction, Rutherford backscattering spectrometry, Interdiffusion, thin film growth, transmission electron microscopy, Epitaxial growth, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-8355 (URN)978-91-554-7055-5 (ISBN)
Public defence
2008-01-18, Polhemssalen, Ångströmlaboratoriet, Lagerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2007-12-18 Created: 2007-12-18 Last updated: 2010-03-09Bibliographically approved
3. Uncovering Magnetic Order in Nanostructured Disordered Materials: A Study of Amorphous Magnetic Layered Structures
Open this publication in new window or tab >>Uncovering Magnetic Order in Nanostructured Disordered Materials: A Study of Amorphous Magnetic Layered Structures
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The scope of this thesis is the study of the interplay between structure and magnetism in amorphous materials. The investigations focus on the growth of amorphous layers and the study of the influence of structural disorder and reduced physical extension on the magnetic properties of thin films and multilayers. The examined magnetic materials are FeZr alloys, as well as other amorphous transition metal alloys such as CoZr and FeCoZr.

Thin films and multilayers of the studied materials were deposited using magnetron sputtering in ultra-high vacuum conditions. Their amorphous structure and layering quality was investigated using X-ray scattering techniques and in several cases with transmission electron microscopy. The chemical composition of the alloys was determined with Rutherford Backscattering Spectrometry. The magnetic properties were investigated using the magneto-optic Kerr effect and SQUID magnetometry, as well as polarized neutron reflectometry and X-ray magnetic circular dicroism measurements.

For FeZr alloys deposited as multilayers with Al2O3 as spacer layer, it was found that Fe-rich nanocrystallites, formed at the metal/oxide interfaces, exert large influence on the magnetic properties. The use of AlZr alloys as buffer layers promotes the growth of highly amorphous FeZr layers. FeZr/AlZr multilayers with good layering quality can also be obtained. The influence of the reduced layer thickness on the magnetic moment, Curie temperature and magnetic dimensionality of the magnetic layers is addressed for FeZr/AlZr multilayers. Thin FeZr layers in these structures are found to belong to the 2D XY dimensionality class. The change of the magnetic moment and Curie temperature with reduced FeZr layer thickness is quantified.

In addition, the induced magnetic moment in the alloy element Zr was investigated in FeZr and CoZr alloy films. The possibility to imprint a preferred magnetization direction during thin film preparation was demonstrated for FeCoZr layers. Lastly, AlZr alloy films were studied with respect to their oxidation stability at room and elevated temperatures, aiming towards development of materials with passivating properties.

Place, publisher, year, edition, pages
Uppsala: Uppsala Universitet, 2011. 124 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 865
Keyword
Amorphous Materials, Magnetism, Amorphous Magnetism, Magnetic Measurements, Thin Films, Multilayers, Thin Film Deposition, Sputtering, FeZr Alloys, AlZr Alloys, X-ray Diffraction, Rutherford Backscattering Spectrometry
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-159913 (URN)978-91-554-8181-0 (ISBN)
Public defence
2011-11-24, Polhelmsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Supervisors
Available from: 2011-11-03 Created: 2011-10-11 Last updated: 2012-02-23Bibliographically approved

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Liebig, AndreasKorelis, PanagiotisLidbaum, HansAndersson, GabriellaLeifer, KlausHjörvarsson, Björgvin

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