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  Phonons in magnetically disordered materials: Magnetic versus phononic time scales

Dutta, B., Körmann, F., Ghosh, S., Sanyal, B., Neugebauer, J., & Hickel, T. (2020). Phonons in magnetically disordered materials: Magnetic versus phononic time scales. Physical Review B, 101(9): 094201. doi:10.1103/PhysRevB.101.094201.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0006-9184-0 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-9B36-F
Genre: Journal Article

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PhysRevB.101.094201.pdf (Supplementary material), 867KB
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 Creators:
Dutta, Biswanath1, 2, Author              
Körmann, Fritz1, 3, Author              
Ghosh, Subhradip4, Author              
Sanyal, Biplab5, Author              
Neugebauer, Jörg6, Author              
Hickel, Tilmann1, Author              
Affiliations:
1Computational Phase Studies, Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863341              
2Materials Science and Engineering, Delft University of Technology, Mekeleweg 2, 2628 CD Delft, The Netherlands, ou_persistent22              
3Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands, ou_persistent22              
4Department of Physics, Indian Institute of Technology Guwahati, India, ou_persistent22              
5Department of Physics and Astronomy, Uppsala University, Box-516 Uppsala, Sweden, ou_persistent22              
6Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863337              

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Free keywords: Atoms; Calculations; Crystal lattices; Magnetic materials; Magnetic moments; Magnetization; Phonons; Vibration analysis, Atomic magnetic moment; Coherent potential approximation; Disordered materials; First principles method; First-principles calculation; Force constant matrix; Qualitative differences; Quantitative modification, Spin fluctuations
 Abstract: The lattice dynamics in magnetic materials, such as Fe depends on the degree of disorder of the atomic magnetic moments and the time scale of spin fluctuations. Using first-principles methods, we have studied this effect by determining the force constant matrix in two limits: (i) When spin fluctuations are much faster than the atom vibrations, their combined impact is captured by a spin-space averaged force constant matrix, (ii) when individual spin fluctuations are sufficiently slow to scatter the phonon modes, the itinerant coherent potential approximation with spin-pair resolved force constants (i.e., φ↑↑,φ↓↓, and φ↑↓) is employed in this paper. The physical consequences for the vibrational spectral functions are analyzed by systematically modifying the input parameters (magnetization and ratio of force constants betweens atoms with equal and opposite spin directions) and by deriving them for the prototype material system bcc Fe from first-principles calculations. In the paramagnetic regime, the two limits yield identical phonon spectra. Below the Curie temperature, however, there are regions in the parametric study that show qualitative differences, including a broadening of the phonon peaks. For bcc Fe, however, the quantitative modifications of phonon frequencies turn out to be small. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.

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Language(s): eng - English
 Dates: 2020-03-02
 Publication Status: Published in print
 Pages: -
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 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1103/PhysRevB.101.094201
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Project name : Funding by the Deutsche Forschungsgemeinschaft (DFG) within the priority Programme No. SPP 1599 is gratefully acknowledged.
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Funding organization : German Research Foundation (DFG) (SPP 1599)

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Title: Physical Review B
  Abbreviation : Phys. Rev. B
Source Genre: Journal
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Publ. Info: Woodbury, NY : American Physical Society
Pages: 10 Volume / Issue: 101 (9) Sequence Number: 094201 Start / End Page: - Identifier: ISSN: 1098-0121
CoNE: https://pure.mpg.de/cone/journals/resource/954925225008