Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The Structural Basis for Magnetic Order in New Manganese Compounds
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
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. , p. 65
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 42
Keywords [en]
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
Keywords [sv]
Oorganisk kemi
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-5746ISBN: 91-554-6215-4 (print)OAI: oai:DiVA.org:uu-5746DiVA, id: diva2:166230
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
List of papers
1. Cycloidal magnetic order in the compound IrMnSi
Open this publication in new window or tab >>Cycloidal magnetic order in the compound IrMnSi
Show others...
2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 71, no 17, p. 174420-Article in journal (Refereed) Published
Abstract [en]

A new compound, IrMnSi, has been synthesized, and its crystal structure and magnetic properties have been investigated by means of neutron powder diffraction, magnetization measurements, and first-principles theory. The crystal structure is found to be of the TiNiSi type (ordered Co2P, space group Pnma). The Mn-projected electronic states are situated at the Fermi level, giving rise to metallic binding, whereas a certain degree of covalent character is observed for the chemical bond between the Ir and Si atoms. A cycloidal, i.e., noncollinear, magnetic structure was observed below 460 K, with the propagation vector q=[0,0,0.4530(5)] at 10 K. The magnetism is dominated by large moments on the Mn sites, 3.8μB∕atom from neutron diffraction. First-principles theory reproduces the propagation vector of the experimental magnetic structure as well as the angles between the Mn moments. The calculations further result in a magnetic moment of 3.2μB for the Mn atoms, whereas the Ir and Si moments are negligible, in agreement with observations. A calculation that more directly incorporates electron-electron interactions improves the agreement between the theoretical and experimental magnetic moments. A band mechanism is suggested to explain the observed magnetic order.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-93494 (URN)10.1103/PhysRevB.71.174420 (DOI)
Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
2. From ordered antiferromagnet to spin glass: a new phase Mn4Ir7-xMnxGe6
Open this publication in new window or tab >>From ordered antiferromagnet to spin glass: a new phase Mn4Ir7-xMnxGe6
2005 In: Journal of Solid State Chemistry, ISSN 0022-4596, Vol. 178, p. 1495-1502Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-92908 (URN)
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2013-03-21
3. Crystal and magnetic structure of Mn3IrSi
Open this publication in new window or tab >>Crystal and magnetic structure of Mn3IrSi
Show others...
2004 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 5, p. 054422-Article in journal (Refereed) Published
Abstract [en]

A new ternary Ir-Mn-Si phase with stoichiometry Mn3IrSi has been synthesized and found to crystallize in the cubic AlAu4-type structure, space group P213 with Z=4, which is an ordered form of the β-Mn structure. The unit cell dimension was determined by x-ray powder diffraction to a=6.4973(3)Å. In addition to the crystal structure, we have determined the magnetic structure and properties using superconducting quantum interference device magnetometry and Rietveld refinements of neutron powder diffraction data. A complex noncollinear magnetic structure is found, with magnetic moments of 2.97(4)μB at 10 K only on the Mn atoms. The crystal structure consists of a triangular network built up by Mn atoms, on which the moments are rotated 120° around the triangle axes. The magnetic unit cell is the same as the crystallographic and carries no net magnetic moment. The Néel temperature was determined to be 210 K. A first-principles study, based on density functional theory in a general noncollinear formulation, reproduces the experimental results with good agreement. The observed magnetic structure is argued to be the result of frustration of antiferromagnetic couplings by the triangular geometry.

National Category
Materials Engineering Inorganic Chemistry Physical Sciences
Identifiers
urn:nbn:se:uu:diva-93493 (URN)10.1103/PhysRevB.69.054422 (DOI)
Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved
4. Structural and magnetic characterization of Mn3IrGe and Mn3Ir(Si1-xGex): experiments and theory
Open this publication in new window or tab >>Structural and magnetic characterization of Mn3IrGe and Mn3Ir(Si1-xGex): experiments and theory
Show others...
2004 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 177, no 11, p. 4058-4066Article 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.

Keywords
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:nbn:se:uu:diva-92910 (URN)10.1016/j.jssc.2004.07.001 (DOI)
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2017-12-14Bibliographically approved
5. Magnetic properties of selected Mn-based transition metal compounds with β-Mn structure: Experiments and theory
Open this publication in new window or tab >>Magnetic properties of selected Mn-based transition metal compounds with β-Mn structure: Experiments and theory
Show others...
2005 In: Physical Review B, ISSN 1098-0121, Vol. 72, p. 144427-Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-92911 (URN)
Available from: 2005-04-19 Created: 2005-04-19 Last updated: 2013-03-21
6. Magnetic short-range order in the new ternary phase Mn8Pd15Si7
Open this publication in new window or tab >>Magnetic short-range order in the new ternary phase Mn8Pd15Si7
Show others...
2005 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 403, no 1-2, p. 19-28Article in journal (Refereed) Published
Abstract [en]

A new compound, Mn8Pd15Si7, is reported to crystallize in a face centered cubic unit cell of dimension a = 12.0141(2) Å, space group, and can thus be classified as a G-phase. The crystal structure was studied by single crystal X-ray diffraction, X-ray and neutron powder diffraction and electron diffraction. A filled Mg6Cu16Si7 type structure was found, corresponding to the Sc11Ir4 type structure. The magnetic properties were investigated by magnetization measurements and Reverse Monte Carlo modeling of low temperature magnetic short-range order (SRO). Dominating near neighbor antiferromagnetic correlations were found between the Mn atoms and geometric frustration in combination with random magnetic interactions via metal sites with partial Mn occupancy were suggested to hinder formation of long-range magnetic order.

Keywords
Intermetallics, Neutron powder diffraction, X-ray diffraction, Magnetic measurements
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-93495 (URN)10.1016/j.jallcom.2005.04.202 (DOI)
Available from: 2005-09-22 Created: 2005-09-22 Last updated: 2017-12-14Bibliographically approved

Open Access in DiVA

fulltext(2316 kB)1336 downloads
File information
File name FULLTEXT01.pdfFile size 2316 kBChecksum MD5
ded735412b8bda426b1a23647ab1ce472bdc56f1054b95a9bffafb35071700d14b0e9b14
Type fulltextMimetype application/pdf
cover(211 kB)44 downloads
File information
File name COVER01.pdfFile size 211 kBChecksum MD5
5d36d24fb6beabb87addb8f6be1133f280f885d7fd8f0a93294e7a0227a111b5b79ae7b7
Type coverMimetype application/pdf
Buy this publication >>

By organisation
Department of Materials Chemistry
Inorganic Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 1336 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1435 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf