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Structural and magnetic characterization of Mn3IrGe and Mn3Ir(Si1-xGex): experiments and theory
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, Theoretical Magnetism.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
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2004 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 177, no 11, 4058-4066 p.Article in journal (Refereed) Published
Abstract [en]

The Structural and magnetic propertiesof a new ternary Ir-Mn-Ge phase, Mn3IrGe, as well as the solid solution Mn3Ir(Si1_xGex), O<x<1, have been investigated by means of X-ray and neutron powder diffraction, magnetization measurements and first principles calculations. The crystal structure is cubic, of the AlAu4-type (an ordered form of the ß-Mn structure), Z = 4. space group P213, and the unit-cell dimension varies linearly with the silicon content. For all compositions, antiferromagnetic

ordering is found below a critical temperature of about 225 K. The magnetic structure is noncollinear, as a result of frustrated magnetic interactions on a triangular network of Mn atoms, on which the moments rotate 120° around the triangle axes. The magnitude of the magnetic moment at 10 K is 3.39(4) µB for Mn3IrGe. The theoretical calculations reproduce with very good accuracy the magnitudes as well as the directions of the experimentally observed magnetic moments.

Place, publisher, year, edition, pages
2004. Vol. 177, no 11, 4058-4066 p.
Keyword [en]
Manganese-iridium germanide, Manganese-indium silicide, Neutron diffraction, Rietveld method, Magnetic structure, Crystal structure, First principles calculations, Susceptibility measurements, Magnetic frustration
National Category
Inorganic Chemistry Materials Engineering
Identifiers
URN: urn:nbn:se:uu:diva-92910DOI: 10.1016/j.jssc.2004.07.001OAI: oai:DiVA.org:uu-92910DiVA: diva2:166227
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2012-03-27Bibliographically approved
In thesis
1. Electronic Structure and Statistical Methods Applied to Nanomagnetism, Diluted Magnetic Semiconductors and Spintronics
Open this publication in new window or tab >>Electronic Structure and Statistical Methods Applied to Nanomagnetism, Diluted Magnetic Semiconductors and Spintronics
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is divided in three parts. In the first part, a study of materials aimed for spintronics applications is presented. More specifically, calculations of the critical temperature in diluted magnetic semiconductors (DMS) and half-metallic ferromagnets are presented using a combination of electronic structure and statistical methods. It is shown that disorder and randomness of the magnetic atoms in DMS materials play a very important role in the determination of the critical temperature.

The second part treats materials in reduced dimensions. Studies of multilayer and trilayer systems are presented. A theoretical model that incorporates interdiffusion in a multilayer is developed that gives better agreement with experimental observations. Using Monte Carlo simulations, the observed magnetic properties in the trilayer system Ni/Cu/Co at finite temperatures are qualitatively reproduced.

In the third part, electronic structure calculations of complex Mn-based compounds displaying noncollinear magnetism are presented. The calculations reproduce with high accuracy the observed magnetic properties in these compounds. Furthermore, a model based on the electronic structure of the necessary conditions for noncollinear magnetism is presented.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. x+70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 32
Keyword
Materials science, spintronics, magnetism, Monte Carlo, critical temperature, exchange interactions, percolation, disorder, noncollinear, electronic structure, Materialvetenskap
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-5732 (URN)91-554-6202-2 (ISBN)
Public defence
2005-04-29, Room 4001, Ångströmlaboratoriet, 10:15
Opponent
Supervisors
Available from: 2005-04-08 Created: 2005-04-08 Last updated: 2013-06-20Bibliographically approved
2. 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 42
Keyword
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
Identifiers
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
Opponent
Supervisors
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2013-06-20Bibliographically approved

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Eriksson, ThereseBergqvist, LarsNordblad, PerEriksson, OlleAndersson, Yvonne

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