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The dynamics of spontaneous hydrogen segregation in LaFe13−xSixHy

Baumfeld, Oliver L. and Gercsi, Zsolt and Krautz, Maria and Gutfleisch, Oliver and Sandeman, Karl G. (2014):
The dynamics of spontaneous hydrogen segregation in LaFe13−xSixHy.
In: Journal of Applied Physics, AIP Publishing LLC, p. 203905, 115, (20), ISSN 0021-8979,
[Online-Edition: http://dx.doi.org/10.1063/1.4879099],
[Article]

Abstract

By means of time-and temperature-dependent magnetization measurements, we demonstrate that the timescale of hydrogen diffusion in partially hydrogenated LaFe13-xSixHy is of the order of hours, when the material is held at temperatures close to its as-prepared Curie temperature, T-C0. The diffusion constant is estimated to be D approximate to 10(-15)-10(-16) m(2) s(-1) at room temperature. We examine the evolution of a magnetically phase-separated state upon annealing for 3 days at a range of temperatures around T-C0 and show that the thermodynamic driving force behind hydrogen diffusion and phase segregation may be attributed to the lower free energy of hydrogen interstitials in the ferromagnetic state relative to the paramagnetic state.

Item Type: Article
Erschienen: 2014
Creators: Baumfeld, Oliver L. and Gercsi, Zsolt and Krautz, Maria and Gutfleisch, Oliver and Sandeman, Karl G.
Title: The dynamics of spontaneous hydrogen segregation in LaFe13−xSixHy
Language: English
Abstract:

By means of time-and temperature-dependent magnetization measurements, we demonstrate that the timescale of hydrogen diffusion in partially hydrogenated LaFe13-xSixHy is of the order of hours, when the material is held at temperatures close to its as-prepared Curie temperature, T-C0. The diffusion constant is estimated to be D approximate to 10(-15)-10(-16) m(2) s(-1) at room temperature. We examine the evolution of a magnetically phase-separated state upon annealing for 3 days at a range of temperatures around T-C0 and show that the thermodynamic driving force behind hydrogen diffusion and phase segregation may be attributed to the lower free energy of hydrogen interstitials in the ferromagnetic state relative to the paramagnetic state.

Journal or Publication Title: Journal of Applied Physics
Volume: 115
Number: 20
Publisher: AIP Publishing LLC
Uncontrolled Keywords: MAGNETIC ENTROPY CHANGE, ELECTRON METAMAGNETIC TRANSITION, COMPOUND, MAGNETOSTRICTION, LA(FE, MN
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Functional Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 17 Nov 2014 09:17
Official URL: http://dx.doi.org/10.1063/1.4879099
Identification Number: doi:10.1063/1.4879099
Funders: The research leading to these results has received funding from the European Community's 7th Framework Programme under Grant Agreement No. 310748 “DRREAM.” , Financial support was acknowledged from The Royal Society (K.G.S.), EPSRC Grant No. EP/G060940/1 (K.G.S. and Z.G.), and an EPSRC DTG studentship is acknowledged by O.L.B.
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