Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4

Yuen Yiu, Manh Duc Le, Rasmus Toft-Petersen, Georg Ehlers, Robert J. McQueeney, David Vaknin

Research output: Contribution to journalJournal articleResearchpeer-review

81 Downloads (Pure)

Abstract

We report on the spinwaves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN = 50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2+ due to splitting of the S = 2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other LiMPO4 (M = Mn, Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.
Original languageEnglish
JournalPhysical Review B
Volume95
Issue number10
Pages (from-to)104409
Number of pages7
ISSN2469-9950
DOIs
Publication statusPublished - 2017
Externally publishedYes

Bibliographical note

©2017 American Physical Society

Cite this

Yiu, Yuen ; Le, Manh Duc ; Toft-Petersen, Rasmus ; Ehlers, Georg ; McQueeney, Robert J. ; Vaknin, David. / Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4. In: Physical Review B. 2017 ; Vol. 95, No. 10. pp. 104409.
@article{81a79135b03344f5914525cdb0c1c364,
title = "Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4",
abstract = "We report on the spinwaves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN = 50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2+ due to splitting of the S = 2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other LiMPO4 (M = Mn, Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.",
author = "Yuen Yiu and Le, {Manh Duc} and Rasmus Toft-Petersen and Georg Ehlers and McQueeney, {Robert J.} and David Vaknin",
note = "{\circledC}2017 American Physical Society",
year = "2017",
doi = "10.1103/PhysRevB.95.104409",
language = "English",
volume = "95",
pages = "104409",
journal = "Physical Review B (Condensed Matter and Materials Physics)",
issn = "1098-0121",
publisher = "American Physical Society",
number = "10",

}

Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4. / Yiu, Yuen; Le, Manh Duc; Toft-Petersen, Rasmus; Ehlers, Georg; McQueeney, Robert J.; Vaknin, David.

In: Physical Review B, Vol. 95, No. 10, 2017, p. 104409.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4

AU - Yiu, Yuen

AU - Le, Manh Duc

AU - Toft-Petersen, Rasmus

AU - Ehlers, Georg

AU - McQueeney, Robert J.

AU - Vaknin, David

N1 - ©2017 American Physical Society

PY - 2017

Y1 - 2017

N2 - We report on the spinwaves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN = 50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2+ due to splitting of the S = 2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other LiMPO4 (M = Mn, Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.

AB - We report on the spinwaves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN = 50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2+ due to splitting of the S = 2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other LiMPO4 (M = Mn, Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.

U2 - 10.1103/PhysRevB.95.104409

DO - 10.1103/PhysRevB.95.104409

M3 - Journal article

VL - 95

SP - 104409

JO - Physical Review B (Condensed Matter and Materials Physics)

JF - Physical Review B (Condensed Matter and Materials Physics)

SN - 1098-0121

IS - 10

ER -