Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Uncovering Magnetic Order in Nanostructured Disordered Materials: A Study of Amorphous Magnetic Layered Structures
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
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 [en]
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: urn:nbn:se:uu:diva-159913ISBN: 978-91-554-8181-0 (print)OAI: oai:DiVA.org:uu-159913DiVA: diva2:447411
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
List of papers
1. Morphology of amorphous Fe91Zr9/Al2O3 multilayers: Dewetting and crystallization
Open this publication in new window or tab >>Morphology of amorphous Fe91Zr9/Al2O3 multilayers: Dewetting and crystallization
Show others...
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.

Keyword
Intermetallic compounds, Amorphous semiconductors, metallic glasses, glasses, X-ray reflectometry, Transmission electron microscopy
National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-11395 (URN)10.1103/PhysRevB.75.214202 (DOI)000247624700041 ()
Available from: 2007-09-11 Created: 2007-09-11 Last updated: 2017-12-11Bibliographically approved
2. Highly amorphous Fe90Zr10 thin films, and the influence of crystallites on the magnetism
Open this publication in new window or tab >>Highly amorphous Fe90Zr10 thin films, and the influence of crystallites on the magnetism
Show others...
2010 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 1, 404-409 p.Article in journal (Refereed) Published
Abstract [en]

A method for depositing highly amorphous, iron-rich Fe100-xZrx thin films on to room temperature substrates is presented. The method involves co-depositing Fe and Zr on to an amorphous AlZr layer. Experimental proof that the structures are completely amorphous is given by transmission electron microscopy and polarized neutron reflectometry. The reflectometry measurements also give an indication of the impact that Fe crystallite impurities have on the magnetic structure and properties of amorphous FeZr. The results are consistent with previous investigations on bulk samples, which showed that crystalline impurities make the magnetic structure more non-collinear.

Keyword
Amorphous films, TEM, Neutron reflectometry, Magnetism
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-139378 (URN)10.1016/j.tsf.2010.07.084 (DOI)000283955200071 ()
Available from: 2010-12-27 Created: 2010-12-23 Last updated: 2017-12-11Bibliographically approved
3. Experimental realization of amorphous two-dimensional XY magnets
Open this publication in new window or tab >>Experimental realization of amorphous two-dimensional XY magnets
2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 2, 024430- p.Article in journal (Refereed) Published
Abstract [en]

The temperature dependence of the magnetization of thin amorphous Fe(89)Zr(11)/Al(78)Zr(22) layerswas investigated. Dimensionality analysis of the ferromagnetic transition of 15 A thick layers yielded critical exponents characteristic of the 2D XY (planar rotor) model. Above the ordering temperature significant polarizability with an applied field is observed, due to the existence of large-scale magnetic correlations, of which the extent and origin have been determined.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-156953 (URN)10.1103/PhysRevB.84.024430 (DOI)000292873700002 ()
Available from: 2011-08-20 Created: 2011-08-11 Last updated: 2017-12-08Bibliographically approved
4. Magnetic and structrural properties of amorphous Fe90Zr10/Al75Zr25 multilayers in the two-dimensional limit.
Open this publication in new window or tab >>Magnetic and structrural properties of amorphous Fe90Zr10/Al75Zr25 multilayers in the two-dimensional limit.
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The magnetic properties of amorphous Fe90 Zr10 /Al75 Zr25 multilayers have been investigated for Fe90 Zr10 bilayer thicknesses in the range t FeZr = 5-20 Å; aiming at enlightening the influence of reduced magnetic layer thickness on the magnetic order. The Al75 Zr25 bilayer thickness is 40 Å, which is thick enough for the interlayer coupling to be negligible. Both the Curie temperature and the magnetic moment decrease (non-linearly) with decreasing thickness of the Fe90 Zr10 bilayer compared to the bulk values. However, the sample with t FeZr = 5 Å has a different behaviour showing that its thickness is below the critical thickness for ferromagnetic order.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-159855 (URN)
Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2013-03-21
5. Violation of Hund's third rule in structurally disordered ferromagnets
Open this publication in new window or tab >>Violation of Hund's third rule in structurally disordered ferromagnets
Show others...
2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 2, 024411- p.Article in journal (Refereed) Published
Abstract [en]

Violation of Hund's third rule caused by structural disorder is observed for the induced magnetic moment of Zr, using x-ray magnetic circular dichroism. The induced spin and orbital magnetic moments are antiparallel in the crystalline state, but parallel in an amorphous state of the investigated Co- and Fe-based materials. First-principles calculations are used to provide physical insight into the dependency of the spin-orbit coupling on the interatomic distance and coordination number.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-156625 (URN)10.1103/PhysRevB.84.024411 (DOI)000292510800008 ()
Available from: 2011-08-06 Created: 2011-08-04 Last updated: 2017-12-08Bibliographically approved
6. Imprinting layer specific magnetic anisotropies in amorphous multilayers
Open this publication in new window or tab >>Imprinting layer specific magnetic anisotropies in amorphous multilayers
Show others...
2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 2, 023918- p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate how layer specific in-plane magnetic anisotropy can be imprinted in amorphous multilayers. The anisotropy is obtained by growing the magnetic layers in the presence of an external field and the anisotropy direction can thereby be arbitrarily chosen for each of the magnetic layers. We used Co68Fe24Zr8 and Al70Zr30 layers as building blocks for demonstrating this effect. The imprinting is expected to be obtainable for a wide range of amorphous materials when grown at temperatures below the magnetic ordering temperature.

Place, publisher, year, edition, pages
AIP, 2009
Keyword
Amourphous multilayers
National Category
Physical Sciences Engineering and Technology
Research subject
Physics of Matter
Identifiers
urn:nbn:se:uu:diva-107510 (URN)10.1063/1.3169523 (DOI)000268613000101 ()
Available from: 2009-08-13 Created: 2009-08-13 Last updated: 2017-12-13Bibliographically approved
7. Structural stability and oxidation resistance of amorphous Zr-Al alloys
Open this publication in new window or tab >>Structural stability and oxidation resistance of amorphous Zr-Al alloys
Show others...
2010 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 401, no 1-3, 38-45 p.Article in journal (Refereed) Published
Abstract [en]

We investigated the structural stability and oxidation resistance of Zr-Al films upon annealing in air. The concentration of Zr was varied from 0 to 100 at.%, with a step of 10 at.%. The films were fabricated using ultra-high vacuum based magnetron sputtering. The as-deposited films with Zr content from 17.3 at.% to 70.7 at.% were found to be X-ray amorphous at room temperature. When exposed to air a thin oxide layer, typically less than 6 nm, is formed. The thickness of the oxide layers increases when the samples are annealed in air and most of these are found to be fully oxidized at 700 degrees C with the formation of crystalline and amorphous oxides on the top of crystalline and amorphous metal films, respectively. The amorphous oxide layers are found to be dense, with well defined thicknesses. An experimental non-equilibrium phase diagram is provided, covering the whole concentration range of the Zr-Al system. (C) 2010 Elsevier B.V. All rights reserved.

National Category
Physical Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-136147 (URN)10.1016/j.jnucmat.2010.03.016 (DOI)000279194300005 ()
Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2017-12-11Bibliographically approved

Open Access in DiVA

fulltext(12535 kB)1079 downloads
File information
File name FULLTEXT02.pdfFile size 12535 kBChecksum SHA-512
5db0f4ee53ffd1d2708586ada09c717eeb82c18fc9198e1ad58f9de1b2a32bc5fae58065486259046e4c26cac1c5414a0e1f2650f5f0c6b40f856177bc926aa8
Type fulltextMimetype application/pdf