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Magnetic Properties of TlCo2Se2 Studied by Mössbauer Spectroscopy
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.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
2004 (English)In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 156/157, no 1-4, 315-319 p.Article in journal (Refereed) Published
Abstract [en]

The quasi two-dimensional antiferromagnetic compound TlCo2Se2 has been studied by 57Fe Mössbauer spectroscopy. Small single crystals have been made with 2% Fe doping. The Mössbauer spectrum, developed below the Néel temperature of 85 K, reveals a distribution of magnetic hyperfine fields (MHF). The fit is reasonably good if we suppose a connection between the values and mutual orientation of the EFG and MHF. That allows us to suggest the existence of a modulation in the helical magnetic structure, discovered earlier by neutron diffraction.

Place, publisher, year, edition, pages
2004. Vol. 156/157, no 1-4, 315-319 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-93789DOI: 10.1023/B:HYPE.0000043247.17411.d2OAI: oai:DiVA.org:uu-93789DiVA: diva2:167380
Available from: 2005-11-17 Created: 2005-11-17 Last updated: 2017-12-14Bibliographically 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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Häggström, LennartBerger, Rolf

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