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Magnetic and interface properties of Fe0.82Ni0.18/Co(001) superlattices
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Physics III.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
2011 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 5, 055301- p.Article in journal (Refereed) Published
Abstract [en]

The thickness dependence of the Fe magnetic hyperfine field and the interfacial intermixing of Fe0.82Ni0.18/Co superlattices, with the same thickness for FeNi and Co layers, have been investigated. A local concentration model using the magnetic hyperfine field values from the [Fe0.82Ni0.18](1-x)Co-x alloys has been used to interpret the field distribution in the superlattices and the Co concentration profiles over the superlattices. A relationship between the Fe magnetic hyperfine field and the Fe magnetic moment has been determined for the unordered [Fe0.82Ni0.18](1-x)Co-x and Fe1-xCox alloys. The magnetic hyperfine fields have been explained using two Fermi contact terms: (i) the core electron term proportional to the Fe magnetic moment with a proportionality constant of -13 T/mu B and (ii) a valence electron term linearly dependent on the Co concentration. The direction of the magnetic moments is found to be in the sample plane except for the 1/1 superlattice, where an angle of about 45 degrees is found.

Place, publisher, year, edition, pages
2011. Vol. 23, no 5, 055301- p.
National Category
Physical Sciences Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-93793DOI: 10.1088/0953-8984/23/5/055301ISI: 000286380800006OAI: oai:DiVA.org:uu-93793DiVA: diva2:167384
Available from: 2005-11-17 Created: 2005-11-17 Last updated: 2011-11-29Bibliographically approved
In thesis
1. 3d Transition Metals Studied by Mössbauer Spectroscopy
Open this publication in new window or tab >>3d Transition Metals Studied by Mössbauer Spectroscopy
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Layered crystals with magnetic elements as Co and Fe have been studied. In TlCo2Se2, where Co atoms in one sheet are separated by Tl and Se from the next Co sheet, magnetic interaction within and between the sheets have been studied. Samples doped with 4% 57Fe replaced Co, show a magnetic spiral character with hyperfine fields in a flower shape in the ab-plane. The magnetic moment of 0.46 μB per Co atom derived from the average field is in good agreement with the result from neutron diffraction. In TlCu1.73Fe0.27Se2 the easy axis of magnetisation is the c-axis. The magnetic moment calculated from the Mössbauer data and SQUID magnetrometry is 0.97 μB per Fe atom with TC = 55(5) K.

Multilayers of different elements have been studied. The effect of vanadium atoms on iron atoms at the interface of FeNi/V multilayers has been determined and the intermixing at the interface has been calculated to be 2-3 monolayers. For FeNi/Co 1/1 monolayer the magnetic hyperfine field (Bhf) is 45° out-of-plane, while for superlattices containing 2 to 5 monolayers it is in the plane. An study on Fe/Co superlattice were done by experimental, theoretical and simulational methods. The Bhf is highest for the Fe at the second layer next to the interface and gets the bulk value in the centre of thicker Fe layers.

Studied magnetic nanoparticles coated with a lipid bilayer (magnetoliposomes) are found to have the magnetite structure but being non-stoichiometric as a result of the manufacturing process. The composition was approximately 32% γ-Fe2O3 and 68% Fe3O4. The oxidation evolution and its effect on magnetic properties of Fe clusters were also studied by means of different techniques.

The extraction and insertion mechanism of lithium in the cathode material Li2FeSiO4 has been monitored by in situ x-ray diffraction and Mössbauer spectroscopy during the first two cycles. The relative amount of Fe+3/ Fe+2 at each end state was in good agreement with the results obtained from electrochemical measurements. A possible explanation to the observed lowering of the potential plateau from 3.10 to 2.80 V occurring during the first cycle, involves a structural rearrangement process in which some of the Li ions and the Fe ions are interchanged.

The behaviour of small amounts of Fe in brass is investigated using Mössbauer spectroscopy. It was shown that a heat treatment can increase the amount of the precipitates of γ-Fe and ~650° C is the optimal treatment for having the highest amount of this phase.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. viii + 86 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 122
Keyword
Physics, Mössbauer Spectroscopy, SQUID Magnetometry, XRD, Layered Structures, Magnetism, Magnetic Superlattices, Nanoparticles, Li-ion Batteries, Brass, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-6163 (URN)91-554-6409-2 (ISBN)
Public defence
2005-12-09, Polhemssalen, Ångström Laboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2005-11-17 Created: 2005-11-17 Last updated: 2009-05-04Bibliographically approved

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