Influence of hydrogenation on the vibrational density of states of magnetocaloric
Abstract
We report on the impact of magnetoelastic coupling on the magnetocaloric properties of LaFe11.4Si1.6H1.6 in terms of the vibrational (phonon) density of states (VDOS), which we determined with 57Fe nuclear resonant inelastic x-ray scattering (NRIXS) measurements and with density functional theory (DFT) based first-principles calculations in the ferromagnetic (FM) low-temperature and paramagnetic (PM) high-temperature phase. In experiments and calculations, we observe pronounced differences in the shape of the Fe-partial VDOS between nonhydrogenated and hydrogenated samples. Furthermore, this shows that hydrogen not only shifts the temperature of the first-order phase transition, but also affects the elastic response of the Fe subsystem significantly. In turn, the anomalous redshift of the Fe VDOS, observed by going to the low-volume PM phase, survives hydrogenation. As a consequence, the change in the Fe-specific vibrational entropy ΔSlat across the phase transition has the same sign as the magnetic and electronic contribution. DFT calculations show that the same mechanism, which is a consequence of the itinerant electron metamagnetism associated with the Fe subsystem, is effective in both the hydrogenated and the hydrogen-free compounds. Although reduced by 50% as compared to the hydrogen-free system, the measured change ΔSlat of 3.2 ± 1.9)J/ kg K across the FM-to-PM transitionmore »
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- Univ. of Duisburg-Essen (Germany)
- TU Darmstadt (Germany)
- Argonne National Lab. (ANL), Lemont, IL (United States)
- European Synchrotron Radiation Facility (ESRF), Grenoble (France)
- Publication Date:
- Research Org.:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); German Research Foundation (DFG)
- OSTI Identifier:
- 1614769
- Alternate Identifier(s):
- OSTI ID: 1600071
- Grant/Contract Number:
- AC02-06CH11357; INST 20876/209-1 FUGG; INST20876/243-1FUGG
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Physical Review B
- Additional Journal Information:
- Journal Volume: 101; Journal Issue: 6; Journal ID: ISSN 2469-9950
- Publisher:
- American Physical Society (APS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; electron-phonon coupling; entropy; magnetic phase transitions; magnetocaloric effect; phonons; density functional theory; first-principles calculations; resonant inelastic x-ray scattering
Citation Formats
Terwey, A., Gruner, M. E., Keune, W., Landers, J., Salamon, S., Eggert, B., Ollefs, K., Brabänder, V., Radulov, I., Skokov, K., Faske, T., Hu, M. Y., Zhao, J., Alp, E. E., Giacobbe, C., Gutfleisch, O., and Wende, H. Influence of hydrogenation on the vibrational density of states of magnetocaloric LaFe11.4Si1.6H1.6. United States: N. p., 2020.
Web. doi:10.1103/PhysRevB.101.064415.
Terwey, A., Gruner, M. E., Keune, W., Landers, J., Salamon, S., Eggert, B., Ollefs, K., Brabänder, V., Radulov, I., Skokov, K., Faske, T., Hu, M. Y., Zhao, J., Alp, E. E., Giacobbe, C., Gutfleisch, O., & Wende, H. Influence of hydrogenation on the vibrational density of states of magnetocaloric LaFe11.4Si1.6H1.6. United States. https://doi.org/10.1103/PhysRevB.101.064415
Terwey, A., Gruner, M. E., Keune, W., Landers, J., Salamon, S., Eggert, B., Ollefs, K., Brabänder, V., Radulov, I., Skokov, K., Faske, T., Hu, M. Y., Zhao, J., Alp, E. E., Giacobbe, C., Gutfleisch, O., and Wende, H. Tue .
"Influence of hydrogenation on the vibrational density of states of magnetocaloric LaFe11.4Si1.6H1.6". United States. https://doi.org/10.1103/PhysRevB.101.064415. https://www.osti.gov/servlets/purl/1614769.
@article{osti_1614769,
title = {Influence of hydrogenation on the vibrational density of states of magnetocaloric LaFe11.4Si1.6H1.6},
author = {Terwey, A. and Gruner, M. E. and Keune, W. and Landers, J. and Salamon, S. and Eggert, B. and Ollefs, K. and Brabänder, V. and Radulov, I. and Skokov, K. and Faske, T. and Hu, M. Y. and Zhao, J. and Alp, E. E. and Giacobbe, C. and Gutfleisch, O. and Wende, H.},
abstractNote = {We report on the impact of magnetoelastic coupling on the magnetocaloric properties of LaFe11.4Si1.6H1.6 in terms of the vibrational (phonon) density of states (VDOS), which we determined with 57Fe nuclear resonant inelastic x-ray scattering (NRIXS) measurements and with density functional theory (DFT) based first-principles calculations in the ferromagnetic (FM) low-temperature and paramagnetic (PM) high-temperature phase. In experiments and calculations, we observe pronounced differences in the shape of the Fe-partial VDOS between nonhydrogenated and hydrogenated samples. Furthermore, this shows that hydrogen not only shifts the temperature of the first-order phase transition, but also affects the elastic response of the Fe subsystem significantly. In turn, the anomalous redshift of the Fe VDOS, observed by going to the low-volume PM phase, survives hydrogenation. As a consequence, the change in the Fe-specific vibrational entropy ΔSlat across the phase transition has the same sign as the magnetic and electronic contribution. DFT calculations show that the same mechanism, which is a consequence of the itinerant electron metamagnetism associated with the Fe subsystem, is effective in both the hydrogenated and the hydrogen-free compounds. Although reduced by 50% as compared to the hydrogen-free system, the measured change ΔSlat of 3.2 ± 1.9)J/ kg K across the FM-to-PM transition contributes with ~35 % significantly and cooperatively to the total isothermal entropy change ΔSiso. Hydrogenation is observed to induce an overall blueshift of the Fe VDOS with respect to the H-free compound; this effect, together with the enhanced Debye temperature observed, is a fingerprint of the hardening of the Fe sublattice by hydrogen incorporation. In addition, the mean Debye velocity of sound of LaFe11.4Si1.6H1.6 was determined from the NRIXS and the DFT data.},
doi = {10.1103/PhysRevB.101.064415},
journal = {Physical Review B},
number = 6,
volume = 101,
place = {United States},
year = {Tue Feb 18 00:00:00 EST 2020},
month = {Tue Feb 18 00:00:00 EST 2020}
}
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