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Synthesis and ab initio calculations of nanolaminated (Cr,Mn)2AlC compounds
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Rhein Westfal TH Aachen, Germany .
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2837-3656
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2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 9Article in journal (Refereed) Published
Abstract [en]

We present an ab initio theoretical analysis of the temperature-dependent stability of inherently nanolaminated (Cr1−xMnx)2AlC. The results indicate energetic stability over the composition range x = 0.0 to 0.5 for temperatures ≥600 K. Corresponding thin film compounds were grown by magnetron sputtering from four elemental targets. X-ray diffraction in combination with analytical transmission electron microscopy, including electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy analysis, revealed that the films were epitaxial (0001)-oriented single-crystals with x up to 0.16.

Place, publisher, year, edition, pages
American Physical Society , 2013. Vol. 87, no 9
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-91544DOI: 10.1103/PhysRevB.87.094113ISI: 000316663700002OAI: diva2:618298

Funding Agencies|European Research Council under the European Community|258509227754|Knut and Alice Wallenberg Foundation||Swedish Research Council|||DFG-SPP 1299|

Available from: 2013-04-26 Created: 2013-04-26 Last updated: 2016-08-31
In thesis
1. Synthesis and Characterization of New MAX Phase Alloys
Open this publication in new window or tab >>Synthesis and Characterization of New MAX Phase Alloys
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This Thesis explores synthesis and characterization of new MAX phase alloys (M = early transition metal, A = A-group element, and X = C or N), based on incorporation of M and X elements previously not considered. My primary focus is on M = Mn for attaining magnetic properties, and on X = O for potential tuning of the transport properties. A recent theoretical study predicted (Cr1-xMnx)2AlC MAX phase to be a stable magnetic nanolaminate. I aimed at realizing this material and through a combinatorial approach based on magnetron sputtering from elemental targets, the first experimental evidence of Mn incorporation (x = 0.16) in a MAX phase is presented. The corresponding MAX phase was also synthesized using cathodic arc film deposition (x = 0.20) and bulk synthesis methods (x = 0.06). The primary characterization techniques were X-ray diffraction and high-resolution (scanning) transmission electron microscopy in combination with energy dispersive X-ray spectroscopy and/or electron energy loss spectroscopy, to obtain a precise local quantification of the MAX phase composition and to perform lattice resolved imaging. For epitaxial film growth of (Cr1-xMnx)2AlC, evidence is presented for the formation of (Cr1-yMny)5Al8, exhibiting a bcc structure with an interplanar spacing matching exactly half a unit cell of the hexagonal MAX phase. Consequently, routinely performed X-ray diffraction symmetric θ-2θ measurements result in peak positions that are identical for the two phases. As (Cr1-yMny)5Al8 is shown to display a magnetic response, its presence needs to be taken into consideration when evaluating the magnetic properties of the MAX phase. Methods  to distinguish between (Cr1-yMny)5Al8 and (Cr1-xMnx)2AlC are also suggested. As different A-element in the MAX phase is theoretically predicted to influence phase stability, attainable level of Mn  incorporation, as well as magnetic properties, thin films of (Cr0.75Mn0.25)2GeC and bulk (Cr0.7Mn0.3)2GaC have also been synthesized. Vibrating sample magnetometry measurements display a magnetic response for all these materials, identifying (Cr,Mn)2AlC, (Cr,Mn)2GeC, and (Cr,Mn)2GaC as the first magnetic MAX phases. The results presented in this Thesis show that A = Al displays the highest magnetic transition temperature (well above room temperature) and A = Ga allows the highest Mn content. The attainable O incorporation in Ti2Al(C1-xOx)MAX phase was explored by arc deposition of Ti2AlC1-y thin films under high vacuum conditions, and solid-state reactions following deposition of understoichiometric TiCz on Al2O3. Ti2Al(C1-xOx)thin films with up to 13 at.% O (x = 0.52) were synthesized, and O was shown to occupy the C lattice site. The obtained O concentration is enough to allow future experimental investigations of the previously suggested (from theory) substantial change in anisotropic electronic properties with increasing O content. The experimental results obtained in this Thesis expand the MAX phase definition and the materials characteristics into new research areas, towards further fundamental understanding and functionalization.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 58 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1573
National Category
Natural Sciences
urn:nbn:se:liu:diva-104829 (URN)10.3384/diss.diva-104829 (DOI)978-91-7519-407-3 (print) (ISBN)
Public defence
2014-03-20, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Available from: 2014-02-27 Created: 2014-02-27 Last updated: 2016-08-31Bibliographically approved

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