Probing Magnetic Excitations in CoII Single-Molecule Magnets by Inelastic Neutron Scattering

Shelby E. Stavretis; Yongqiang Cheng; Luke L. Daemen; Craig M. Brown; Duncan H. Moseley; Eckhard Bill; Mihail Atanasov; Anibal J. Ramirez-Cuesta; Frank Neese; Zi Ling Xue

doi:10.1002/ejic.201801088

Probing Magnetic Excitations in Co^II Single-Molecule Magnets by Inelastic Neutron Scattering

Shelby E. Stavretis, Yongqiang Cheng, Luke L. Daemen, Craig M. Brown, Duncan H. Moseley, Eckhard Bill, Mihail Atanasov, Anibal J. Ramirez-Cuesta, Frank Neese, Zi Ling Xue

Research output: Contribution to journal › Article › peer-review

15 Scopus citations

Abstract

Co(acac)₂(H₂O)₂ (1, acac = acetylacetonate), a transition metal complex (S = 3/2), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac)₂(D₂O)₂ (1-d₄) and Co(acac-d₇)₂(D₂O)₂ (1-d₁₈) in approximately D_4h symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy M_S = ±1/2 (ϕ_1,2) and higher energy M_S = ±3/2 (ϕ_3,4) states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1-d₄ and 1-d₁₈. Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, M_S = –1/2 (ϕ₁) → M_S = +1/2 (ϕ₂), in 1-d₁₈. This is a rare study of the M_S = –1/2 → M_S = +1/2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, M_S = ±1/2 (ϕ_1,2) → M_S = ±3/2 (ϕ_3,4) in both 1-d₄ and 1-d₁₈, by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.

Original language	English
Pages (from-to)	1119-1127
Number of pages	9
Journal	European Journal of Inorganic Chemistry
Volume	2019
Issue number	8
DOIs	https://doi.org/10.1002/ejic.201801088
State	Published - Feb 28 2019

Funding

The authors thank financial support by the US National Science Foundation (CHE-1633870 to Z-L. X.), Deutsche Forschungsge-meinschaft (E. B., M. A., and F. N.), and a Shull Wollan Center Graduate Research Fellowship (S. E. S). Acknowledgment is also made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this workand to Dr. Daniel M. Pajerowski for help. The research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Computational resources for the VASP DFT and INS calculations were made available through the VirtuES and ICEMAN projects, funded by the Laboratory Directed Research and Development at ORNL.

Funders	Funder number
Scientific User Facilities Division
Shull Wollan Center
National Science Foundation	1633870, CHE-1633870
U.S. Department of Energy
Basic Energy Sciences
Oak Ridge National Laboratory
American Chemical Society Petroleum Research Fund
Laboratory Directed Research and Development
Deutsche Forschungsgemeinschaft

Keywords

Cobalt
DFT phonon calculations
Inelastic neutron scattering
Phonons
Zero-field splitting

Access to Document

10.1002/ejic.201801088

Cite this

@article{bacb4c8cd8cf4afb99a525ad73fff70c,

title = "Probing Magnetic Excitations in CoII Single-Molecule Magnets by Inelastic Neutron Scattering",

abstract = "Co(acac)2(H2O)2 (1, acac = acetylacetonate), a transition metal complex (S = 3/2), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac)2(D2O)2 (1-d4) and Co(acac-d7)2(D2O)2 (1-d18) in approximately D4h symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy MS = ±1/2 (ϕ1,2) and higher energy MS = ±3/2 (ϕ3,4) states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1-d4 and 1-d18. Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, MS = –1/2 (ϕ1) → MS = +1/2 (ϕ2), in 1-d18. This is a rare study of the MS = –1/2 → MS = +1/2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, MS = ±1/2 (ϕ1,2) → MS = ±3/2 (ϕ3,4) in both 1-d4 and 1-d18, by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.",

keywords = "Cobalt, DFT phonon calculations, Inelastic neutron scattering, Phonons, Zero-field splitting",

author = "Stavretis, {Shelby E.} and Yongqiang Cheng and Daemen, {Luke L.} and Brown, {Craig M.} and Moseley, {Duncan H.} and Eckhard Bill and Mihail Atanasov and Ramirez-Cuesta, {Anibal J.} and Frank Neese and Xue, {Zi Ling}",

note = "Publisher Copyright: {\textcopyright} 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim",

year = "2019",

month = feb,

day = "28",

doi = "10.1002/ejic.201801088",

language = "English",

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journal = "European Journal of Inorganic Chemistry",

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publisher = "Wiley-VCH Verlag",

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TY - JOUR

T1 - Probing Magnetic Excitations in CoII Single-Molecule Magnets by Inelastic Neutron Scattering

AU - Stavretis, Shelby E.

AU - Cheng, Yongqiang

AU - Daemen, Luke L.

AU - Brown, Craig M.

AU - Moseley, Duncan H.

AU - Bill, Eckhard

AU - Atanasov, Mihail

AU - Ramirez-Cuesta, Anibal J.

AU - Neese, Frank

AU - Xue, Zi Ling

PY - 2019/2/28

Y1 - 2019/2/28

N2 - Co(acac)2(H2O)2 (1, acac = acetylacetonate), a transition metal complex (S = 3/2), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac)2(D2O)2 (1-d4) and Co(acac-d7)2(D2O)2 (1-d18) in approximately D4h symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy MS = ±1/2 (ϕ1,2) and higher energy MS = ±3/2 (ϕ3,4) states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1-d4 and 1-d18. Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, MS = –1/2 (ϕ1) → MS = +1/2 (ϕ2), in 1-d18. This is a rare study of the MS = –1/2 → MS = +1/2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, MS = ±1/2 (ϕ1,2) → MS = ±3/2 (ϕ3,4) in both 1-d4 and 1-d18, by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.

AB - Co(acac)2(H2O)2 (1, acac = acetylacetonate), a transition metal complex (S = 3/2), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac)2(D2O)2 (1-d4) and Co(acac-d7)2(D2O)2 (1-d18) in approximately D4h symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy MS = ±1/2 (ϕ1,2) and higher energy MS = ±3/2 (ϕ3,4) states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1-d4 and 1-d18. Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, MS = –1/2 (ϕ1) → MS = +1/2 (ϕ2), in 1-d18. This is a rare study of the MS = –1/2 → MS = +1/2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, MS = ±1/2 (ϕ1,2) → MS = ±3/2 (ϕ3,4) in both 1-d4 and 1-d18, by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.

KW - Cobalt

KW - DFT phonon calculations

KW - Inelastic neutron scattering

KW - Phonons

KW - Zero-field splitting

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DO - 10.1002/ejic.201801088

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JO - European Journal of Inorganic Chemistry

JF - European Journal of Inorganic Chemistry

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