Cai, Qingan; Zhang, Yuemei; Luong, Diana; Tulk, Christopher A.; Fokwa, Boniface P. T.; Li, Chen
Spin–Phonon Interactions and Anharmonic Lattice Dynamics in Fe3GeTe2 Journal Article
In: Advanced Physics Research, no. 2200089, 2023.
Abstract | Links | BibTeX | Tags: anharmonicity, DFT, high pressure, magnon-phonon, Raman, selenide
@article{Cai2023,
title = {Spin\textendashPhonon Interactions and Anharmonic Lattice Dynamics in Fe3GeTe2},
author = {Qingan Cai and Yuemei Zhang and Diana Luong and Christopher A. Tulk and Boniface P.T. Fokwa and Chen Li},
url = {https://onlinelibrary.wiley.com/doi/10.1002/apxr.202200089},
doi = {10.1002/apxr.202200089},
year = {2023},
date = {2023-03-24},
urldate = {2023-03-24},
journal = {Advanced Physics Research},
number = {2200089},
abstract = {Raman scattering is performed on Fe3GeTe2 (FGT) at temperatures from 8 to 300 K and under pressures from the ambient pressure to 9.43 GPa. Temperature-dependent and pressure-dependent Raman spectra are reported. The results reveal respective anomalous softening and moderate stiffening of the two Raman active modes as a result of the increase of pressure. The anomalous softening suggests anharmonic phonon dynamics and strong spin\textendashphonon coupling. Pressure-dependent density functional theory and phonon calculations are conducted and used to study the magnetic properties of FGT and assign the observed Raman modes E^2_2g and A^1_1g. The calculations proved the strong spin\textendashphonon coupling for the E^2_2g mode. In addition, a synergistic interplay of pressure-induced reduction of spin exchange interactions and spin\textendashorbit coupling effect accounts for the softening of the E^2_2g mode as pressure increases.},
keywords = {anharmonicity, DFT, high pressure, magnon-phonon, Raman, selenide},
pubstate = {published},
tppubtype = {article}
}
Raman scattering is performed on Fe3GeTe2 (FGT) at temperatures from 8 to 300 K and under pressures from the ambient pressure to 9.43 GPa. Temperature-dependent and pressure-dependent Raman spectra are reported. The results reveal respective anomalous softening and moderate stiffening of the two Raman active modes as a result of the increase of pressure. The anomalous softening suggests anharmonic phonon dynamics and strong spin–phonon coupling. Pressure-dependent density functional theory and phonon calculations are conducted and used to study the magnetic properties of FGT and assign the observed Raman modes E^2_2g and A^1_1g. The calculations proved the strong spin–phonon coupling for the E^2_2g mode. In addition, a synergistic interplay of pressure-induced reduction of spin exchange interactions and spin–orbit coupling effect accounts for the softening of the E^2_2g mode as pressure increases.
Cai, Qingan; McIntire, Michael; Daemen, Luke L.; Li, Chen; Chronister, Eric L.
Pressure- and temperature-dependent inelastic neutron scattering study of the phase transition and phonon lattice dynamics in para-terphenyl Journal Article
In: Physical Chemistry Chemical Physics, vol. 23, pp. 8792, 2021.
Abstract | Links | BibTeX | Tags: high pressure, phonon, Raman
@article{Cai2021,
title = {Pressure- and temperature-dependent inelastic neutron scattering study of the phase transition and phonon lattice dynamics in para-terphenyl},
author = {Qingan Cai and Michael McIntire and Luke L. Daemen and Chen Li and Eric L. Chronister},
url = {https://pubs.rsc.org/en/content/articlelanding/2021/cp/d1cp00190f#!divAbstract},
doi = {10.1039/D1CP00190F},
year = {2021},
date = {2021-03-24},
journal = {Physical Chemistry Chemical Physics},
volume = {23},
pages = {8792},
abstract = {Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0\textendash1.51 kbar and 10\textendash30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, is out of the pressure and temperature range of this study.},
keywords = {high pressure, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Inelastic neutron scattering has been performed on para-terphenyl at temperatures from 10 to 200 K and under pressures from the ambient pressure to 1.51 kbar. The temperature dependence of phonons, especially low-frequency librational bands, indicates strong anharmonic phonon dynamics. The pressure- and temperature-dependence of the phonon modes suggest a lack of phase transition in the region of 0–1.51 kbar and 10–30 K. Additionally, the overall lattice dynamics remains similar up to 200 K under the ambient pressure. The results suggest that the boundary between the ordered triclinic phase and the third solid phase, reported at lower temperatures and higher pressures, is out of the pressure and temperature range of this study.
Lan, T; Li, Chen W; Fultz, B
In: Physical Review B, vol. 86, no. 13, pp. 134302, 2012.
Abstract | Links | BibTeX | Tags: anharmonicity, first-principles, phonon, Raman
@article{lan_phonon_2012,
title = {Phonon anharmonicity of rutile SnO 2studied by Raman spectrometry and first principles calculations of the kinematics of phonon-phonon interactions},
author = {T Lan and Chen W Li and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.86.134302},
doi = {10.1103/PhysRevB.86.134302},
year = {2012},
date = {2012-10-01},
journal = {Physical Review B},
volume = {86},
number = {13},
pages = {134302},
abstract = {Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.},
keywords = {anharmonicity, first-principles, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.
Li, Chen W; McKerns, M M; Fultz, B
A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures Journal Article
In: Journal of the American Ceramic Society, vol. 94, no. 1, pp. 224-229, 2010.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, oxide, phonon, Raman
@article{li_raman_2010,
title = {A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures},
author = {Chen W Li and M M McKerns and B Fultz},
url = {http://doi.wiley.com/10.1111/j.1551-2916.2010.04057.x},
doi = {10.1111/j.1551-2916.2010.04057.x},
year = {2010},
date = {2010-01-01},
journal = {Journal of the American Ceramic Society},
volume = {94},
number = {1},
pages = {224-229},
abstract = {Raman spectra of monoclinic zirconia (ZrO2) were measured at temperatures of up to 950 K. Temperature‐dependent Raman peak shifts and broadenings were reported and compared with prior results on hafnia...},
keywords = {anharmonicity, high temperature, oxide, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of monoclinic zirconia (ZrO2) were measured at temperatures of up to 950 K. Temperature‐dependent Raman peak shifts and broadenings were reported and compared with prior results on hafnia...
Li, Chen W; McKerns, M M; Fultz, B
Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures Journal Article
In: Physical Review B, vol. 80, no. 5, pp. 1745, 2009.
Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, oxide, phonon, Raman
@article{li_raman_2009,
title = {Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures},
author = {Chen W Li and M M McKerns and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.80.054304},
doi = {10.1103/PhysRevB.80.054304},
year = {2009},
date = {2009-08-01},
journal = {Physical Review B},
volume = {80},
number = {5},
pages = {1745},
abstract = {Raman spectra of monoclinic hafnium oxide $(textbackslashtextHfO_2)$ were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and broadenings, it was found that modes involving changes in oxygen-oxygen bond length were the most anharmonic. The hafnium-dominated modes were more quasiharmonic and showed less broadening with temperature. Comparatively, the oxygen-dominated modes were more influenced by the cubic term in the interatomic potential than the hafnium-dominated modes. An approximately quadratic correlation was found between phonon-line broadening and softening.},
keywords = {anharmonicity, high temperature, oxide, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of monoclinic hafnium oxide $(textbackslashtextHfO_2)$ were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and broadenings, it was found that modes involving changes in oxygen-oxygen bond length were the most anharmonic. The hafnium-dominated modes were more quasiharmonic and showed less broadening with temperature. Comparatively, the oxygen-dominated modes were more influenced by the cubic term in the interatomic potential than the hafnium-dominated modes. An approximately quadratic correlation was found between phonon-line broadening and softening.