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Tuning the Curie temperature of FeCo compounds by tetragonal distortion
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
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2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 10, 102404- p.Article in journal (Refereed) Published
Abstract [en]

Combining density-functional theory calculations with a classical Monte Carlo method, we show that for B2-type FeCo compounds, tetragonal distortion gives rise to a strong reduction of the Curie temperature T-C. The T-C monotonically decreases from 1575K (for c/a = 1) to 940K (for c/a = root 2). We find that the nearest neighbor Fe-Co exchange interaction is sufficient to explain the c/a behavior of the T-C. Combination of high magnetocrystalline anisotropy energy with a moderate TC value suggests tetragonal FeCo grown on the Rh substrate with c/a = 1.24 to be a promising material for heat-assisted magnetic recording applications.

Place, publisher, year, edition, pages
2013. Vol. 103, no 10, 102404- p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-211902DOI: 10.1063/1.4819773ISI: 000324389700031OAI: oai:DiVA.org:uu-211902DiVA: diva2:669371
Available from: 2013-12-03 Created: 2013-12-03 Last updated: 2015-04-17Bibliographically approved
In thesis
1. Ab initio Studies on Exchange Interactions in Metals and Correlated Oxides
Open this publication in new window or tab >>Ab initio Studies on Exchange Interactions in Metals and Correlated Oxides
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A report is given on the implementation of a frozen magnon technique in the FLAPW code FLEUR, showing that the procedure reduced computational costs compared with a previously implemented method, while delivering accurate results. Furthermore a generalisation was made of the well known one lattice formula that connects the total energy differences of spin-spirals to the adiabatic magnon excitation energies to multiple lattice systems.

The implemented method was applied to B2 structured FeCo to investigate the changes of the Curie temperature with a tetragonal distortion and it was found that the FeCo films grown on Rh have characteristics that makes it a good candidate for HAMR storage media. The method was also applied to a selection of spin-gapless semiconductors in order to investigate their magnetic properties. It was found that all of the studied materials have a Curie temperature well above room temperature and excellent agreement with experimental results was obtained for the material Mn2CoAl that has been synthesised.

Finally, the implemented frozen magnon method was adjusted to include constraining fields to restrict the directions of the magnetic moments. It was shown that this procedure significantly improved the agreement between the dispersion for all considered spin-spiral configuration and introduced significant adjustments of the exchange parameters. However for other materials, such as bcc-Fe, such corrections yield worse results and, motivated by the need for a consistent method, we considered a self consistent spin-spiral based method to extract the exchange parameters from the inverse transverse static magnetic susceptibility. Preliminary results show that the newly implemented method gives results close to the corrected frozen magnon method for FeCo and results close to the uncorrected frozen magnon method for bcc Fe and thus provides a consistent improvement over the two previously used methods.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 53 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1236
National Category
Condensed Matter Physics
urn:nbn:se:uu:diva-246766 (URN)978-91-554-9190-1 (ISBN)
Public defence
2015-04-17, room 10132, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Available from: 2015-03-26 Created: 2015-03-10 Last updated: 2015-04-17Bibliographically approved

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