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The magnetic structure of TlCrTe2
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.
2005 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 403, no 1-2, 71-75 p.Article in journal (Refereed) Published
Abstract [en]

The magnetic structure of the antiferromagnetic layer compound TlCrTe2 has been determined by neutron powder diffraction. The magnetic moments on chromium are aligned along the c axis in the hexagonal cell and couple ferromagnetically within the sheets. Adjacent layers couple antiferromagnetically below the transition temperature of 145 K. This gives rise to a doubling of the c axis for describing the magnetic unit cell. The magnetic moment of the chromium atom is 3.39(4) μB at 10 K in line with localised 3d3 of Cr3+. Electronic structure calculations on TlCrTe2 of density–functional type (GGA) show a clear driving force for the ferromagnetic coupling in the layers and a lowering of the total energy upon magnetic ordering, the theoretical magnetic moment being in almost quantitative agreement with the experiment.

Place, publisher, year, edition, pages
2005. Vol. 403, no 1-2, 71-75 p.
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-93546DOI: 10.1016/j.jallcom.2005.05.028OAI: oai:DiVA.org:uu-93546DiVA: diva2:167054
Available from: 2005-10-07 Created: 2005-10-07 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Chemical Tuning of the Magnetic Interactions in Layer Structures
Open this publication in new window or tab >>Chemical Tuning of the Magnetic Interactions in Layer Structures
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Thin metal films have found their use in many magnetic devices. They form pseudo two-dimensional systems, where the mechanisms for the magnetic interactions between the layers are not completely understood. Layered crystal structures have an advantage over such artificial systems, since the layers can be strictly mono-atomic without any unwanted admixture. In this study, some model systems of layered magnetic crystal structures and their solid solutions have been investigated by x-ray and neutron diffraction, Mössbauer and electron spectroscopy, heat-capacity and magnetic measurements, and first-principle electronic structure calculations, with the goal of deepening our understanding through controlled chemical synthesis.

The compounds TlCo2S2, TlCo2Se2 and their solid solution TlCo2Se2-xSx, all containing well separated cobalt atom sheets, order with the moments ferromagnetically aligned within the sheets. In TlCo2S2, the net result is ferromagnetism, while TlCo2Se2 exhibits antiferromagnetism. The inter-layer distance is crucial for the long-range coupling, and it was varied systematically through Se-S substitution. The incommensurate helical magnetic structure found for TlCo2Se2 (x = 0) prevails in the composition range 0 ≤ x ≤ 1.5 but the pitch of the helix changes. The accompanying reduction in inter-layer distance on sulphur substitution varies almost linearly with the coupling angle of the helix. An additional competing commensurate helix (90°) appears in the medium composition range (found for x = 0.5 and 1.0).

The systems TlCo2-xMexSe2 show helical magnetic ordering for Me = Fe or Cu, while a collinear antiferromagnetic structure occurs for Me = Ni. Magnetic order is created by iron substitution for copper in the Pauli paramagnetic TlCu2Se2, but now with the moments perpendicular to the metal sheets.

TlCrTe2 forms a quite different crystal structure, with intra-layer ferromagnetic alignment and net collinear antiferromagnetism. In contrast to the other phases, the values of the moments conform well to a localised model for Cr3+.

Place, publisher, year, edition, pages
Uppsala: Institutionen för materialkemi, 2005. 63 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 97
Keyword
Inorganic chemistry, neutron powder diffraction, magnetometry, layered magnetic structure, incommensurate helical structure, ThCr2Si2 type structure, antiferromagnetism, ferromagnetism, electronic structure calculations, Oorganisk kemi
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-5973 (URN)91-554-6357-6 (ISBN)
Public defence
2005-10-28, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-10-07 Created: 2005-10-07 Last updated: 2013-09-13Bibliographically approved

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Berger, Rolf

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