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From ordered antiferromagnet to spin glass: a new phase Mn4Ir7-xMnxGe6
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
2005 In: Journal of Solid State Chemistry, ISSN 0022-4596, Vol. 178, 1495-1502 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2005. Vol. 178, 1495-1502 p.
URN: urn:nbn:se:uu:diva-92908OAI: oai:DiVA.org:uu-92908DiVA: diva2:166225
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2013-03-21
In thesis
1. The Structural Basis for Magnetic Order in New Manganese Compounds
Open this publication in new window or tab >>The Structural Basis for Magnetic Order in New Manganese Compounds
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials with new or improved properties are crucial for technological development. To provide the foundation for future successful products, it is important to prepare and characterise new chemical compounds that could show unusual properties. The properties of magnetic materials are closely related to their crystal, magnetic and electronic structures. This thesis focuses on the novel synthesis and structural characterisation of a number of new ternary or pseudo-ternary silicides and germanides of manganese with iridium, cobalt or palladium. To provide a more complete picture of the complex magnetic properties, crystal and magnetic structure refinements by the Rietveld method of X-ray and neutron powder diffraction data are complemented by single-crystal X-ray diffraction, electron diffraction, magnetisation measurements and Reverse Monte Carlo simulations of magnetic short-range order. The experimental results are corroborated by first-principles electronic structure and total energy calculations.

A commensurate non-collinear antiferromagnetic structure is found for most compounds of the solid solution Mn3Ir1-yCoySi1-xGex. The non-collinearity is a result of geometric frustration in a crystal structure with magnetic Mn atoms located on a three-dimensional network of triangles. The close structural similarity to the β-modification of elemental manganese, which does not order magnetically, inspired a closer theoretical comparison of the Mn3Ir1-yCoySi1-xGex propertieswith β-Mn.

Magnetic frustration is also observed for Mn4Ir7-xMnxGe6, and is an important factor underlying the dramatic change from commensurate antiferromagnetic order to spin glass properties induced by a small variation in Mn concentration. Magnetic short-range order with dominant antiferromagnetic correlation is observed for Mn8Pd15Si7, and results from a random distribution of Mn atoms in-between the geometrically frustrated magnetic moments on the Mn octahedra.

An incommensurate cycloidal magnetic structure, observed for IrMnSi, is stabilised by an electronic structure effect, which also accounts for the non-collinearity of the Mn3IrSi type magnetic structure.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 65 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 42
Inorganic chemistry, Crystal structure, Magnetic structure, Manganese compounds, Transition metal silicides, Transition metal germanides, Magnetic frustration, Neutron powder diffraction, X-ray diffraction, Magnetisation measurements, DFT, Oorganisk kemi
National Category
Inorganic Chemistry
urn:nbn:se:uu:diva-5746 (URN)91-554-6215-4 (ISBN)
Public defence
2005-05-12, Häggsalen, The Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2013-06-20Bibliographically approved

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