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Phonon confinement and spin-phonon coupling in tensile-strained ultrathin EuO films

Ramu Pradip, Przemysław Piekarz, Dániel G. Merkel, Jochen Kalt, Olga Waller, Aleksandr I. Chumakov, Rudolf Rüffer, Andrzej M. Oles, Krzysztof Parlinski, Tilo Baumbach and Svetoslav Stankov

Article (2019)

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Abstract

Reducing the material sizes to the nanometer length scale leads to drastic modifications of the propagating lattice excitations (phonons) and their interactions with electrons and magnons. In EuO, a promising material for spintronic applications in which a giant spin-phonon interaction is present, this might imply a reduction of the degree of spin polarization in thin films. Therefore, a comprehensive investigation of the lattice dynamics and spin-phonon interaction in EuO films is necessary for practical applications. We report a systematic lattice dynamics study of ultrathin EuO(001) films using nuclear inelastic scattering on the Mossbauer-active isotope 151Eu and first-principles theory. The films were epitaxially grown on YAlO3(110), which induces a tensile strain of ca. 2%. By reducing the EuO layer thickness from 8 nm to a sub-monolayer coverage, the Eu-partial phonon density of states (PDOS) reveals a gradual enhancement of the number of low-energy phonon states and simultaneous broadening and suppression of the peaks. These deviations from bulk features lead to significant anomalies in the vibrational thermodynamic and elastic properties calculated from the PDOS. The experimental results, supported by first-principles theory, unveil a reduction of the strength of the spin-phonon interaction in the tensile-strained EuO by a factor of four compared to a strain-free lattice.

Department: Department of Engineering Physics
Funders: Helmholtz Association, BMBF, Narodowe Centrum Nauki (NCN), Alexander von Humboldt Fellowship (Humboldt-Forschungspreis), Narodowe Centrum Nauki (NCN, National Science Centre), Polish Ministry of Science and High Education
Grant number: VH-NG-625, 05K16VK4, 016/23/B/ ST3/00839, 2017/25/B/ST3/02586, IR/WK/2016/19
PolyPublie URL: https://publications.polymtl.ca/5094/
Journal Title: Nanoscale (vol. 11, no. 22)
Publisher: Royal Society of Chemistry
DOI: 10.1039/c9nr01931f
Official URL: https://doi.org/10.1039/c9nr01931f
Date Deposited: 26 Sep 2022 12:58
Last Modified: 09 Apr 2024 17:26
Cite in APA 7: Pradip, R., Piekarz, P., Merkel, D. G., Kalt, J., Waller, O., Chumakov, A. I., Rüffer, R., Oles, A. M., Parlinski, K., Baumbach, T., & Stankov, S. (2019). Phonon confinement and spin-phonon coupling in tensile-strained ultrathin EuO films. Nanoscale, 11(22), 10968-10976. https://doi.org/10.1039/c9nr01931f

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