Effect of pressure, temperature, fluorine doping, and rare earth elements on the phonon density of states of $L$FeAsO studied by nuclear inelastic scattering

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Effect of pressure, temperature, fluorine doping, and rare earth elements on the phonon density of states of $L$ FeAsO studied by nuclear inelastic scattering

I. Sergueev, R. P. Hermann, D. Bessas, U. Pelzer, M. Angst, W. Schweika, M. A. McGuire, A. S. Sefat, B. C. Sales, D. Mandrus, and R. Rüffer

Phys. Rev. B 87, 064302 – Published 25 February 2013

Abstract

We have performed systematic studies of the lattice dynamics in $L$ FeAsO ( $L = La$ , Ce, Pr, Nd, Sm) in the parent and in the $\sim$ 10% F-doped compounds as a function of pressure and temperature. We have found that the modifications in the partial Fe density of phonon states are mainly governed by the Fe-As bond length. The change of this bond length explains the change of the Fe density of phonon states above 25 meV. We further observe anomalies in the behavior of the phonon mode near 16 meV. In the parent phase, this mode softens anomalously upon cooling through the structural phase transition. Upon F doping, this mode hardens indicating a strong electron-phonon coupling. This suggests that the corresponding phonons play an important role in the competition between superconductivity and magnetism in these materials.

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Received 7 January 2013

DOI:https://doi.org/10.1103/PhysRevB.87.064302

Authors & Affiliations

I. Sergueev^1,2,3,*, R. P. Hermann^2,4, D. Bessas^2,4,1, U. Pelzer¹, M. Angst^2,5, W. Schweika^2,6, M. A. McGuire⁷, A. S. Sefat⁷, B. C. Sales⁷, D. Mandrus^7,8, and R. Rüffer¹

¹European Synchrotron Radiation Facility (ESRF), P.O. Box 220, F-38043 Grenoble, France
²Jülich Center for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
³Deutsches Elektronen-Synchrotron, D-22607 Hamburg, Germany
⁴Faculté des Sciences, Université de Liège, B-4000 Liège, Belgium
⁵Experimental Physics IVC, RWTH Aachen University, D-52056 Aachen, Germany
⁶European Spallation Source AB, S-22100 Lund, Sweden
⁷Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁸Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA

^*ilya.sergeev@desy.de

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Vol. 87, Iss. 6 — 1 February 2013

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