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Moment-Volume Coupling in La(Fe1−x Si x )13

Gruner, Markus E. and Keune, Werner and Landers, Joachim and Salamon, Soma and Krautz, Maria and Zhao, Jiyong and Hu, Michael Y. and Toellner, Thomas and Alp, Esen E. and Gutfleisch, Oliver and Wende, Heiko (2018):
Moment-Volume Coupling in La(Fe1−x Si x )13.
In: physica status solidi (b), Wiley-VCH Verlag GmbH, Weinheim, p. 1700465, 255, (2), ISSN 03701972,
DOI: 10.1002/pssb.201700465,
[Online-Edition: https://doi.org/10.1002/pssb.201700465],
[Article]

Abstract

We investigate the origin of the volume change and magnetoelastic interaction observed at the magnetic first-order transition in the magnetocaloric system La(Fe1-xSix)(13) by means of first-principles calculations combined with the fixed-spin moment approach. We find that the volume of the system varies with the square of the average local Fe moment, which is significantly smaller in the spin disordered configurations compared to the ferromagnetic ground state. The vibrational density of states obtained for a hypothetical ferromagnetic state with artificially reduced spin-moments compared to a nuclear inelastic X-ray scattering measurement directly above the phase transition reveals that the anomalous softening at the transition essentially depends on the same moment-volume coupling mechanism. In the same spirit, the dependence of the average local Fe moment on the Si content can account for the occurence of first- and second-order transitions in the system.

Item Type: Article
Erschienen: 2018
Creators: Gruner, Markus E. and Keune, Werner and Landers, Joachim and Salamon, Soma and Krautz, Maria and Zhao, Jiyong and Hu, Michael Y. and Toellner, Thomas and Alp, Esen E. and Gutfleisch, Oliver and Wende, Heiko
Title: Moment-Volume Coupling in La(Fe1−x Si x )13
Language: English
Abstract:

We investigate the origin of the volume change and magnetoelastic interaction observed at the magnetic first-order transition in the magnetocaloric system La(Fe1-xSix)(13) by means of first-principles calculations combined with the fixed-spin moment approach. We find that the volume of the system varies with the square of the average local Fe moment, which is significantly smaller in the spin disordered configurations compared to the ferromagnetic ground state. The vibrational density of states obtained for a hypothetical ferromagnetic state with artificially reduced spin-moments compared to a nuclear inelastic X-ray scattering measurement directly above the phase transition reveals that the anomalous softening at the transition essentially depends on the same moment-volume coupling mechanism. In the same spirit, the dependence of the average local Fe moment on the Si content can account for the occurence of first- and second-order transitions in the system.

Journal or Publication Title: physica status solidi (b)
Volume: 255
Number: 2
Publisher: Wiley-VCH Verlag GmbH, Weinheim
Uncontrolled Keywords: density functional theory, Invar effect, La-Fe-Si compounds, magnetocaloric effect, magnetoelastic coupling, nuclear resonanant inelastic X-ray scattering
Divisions: 11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences
Date Deposited: 12 Mar 2018 10:34
DOI: 10.1002/pssb.201700465
Official URL: https://doi.org/10.1002/pssb.201700465
Funders: This work has been supported by the Deutsche Forschungsgemeinschaft in the framework of the priority program SPP 1599 (GR3498/3-2, GU514/6-2, WE2623/12-2), SPP 1681 (WE2623/7-1), FOR 1509 (WE2623/13-2), and by Stiftung Mercator (MERCUR)., Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE No. DE-AC02-05CH11231).
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