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High-field/high-frequency electron spin resonances of Fe-doped β-Ga2 O3 by terahertz generalized ellipsometry : Monoclinic symmetry effects

Richter, Steffen LU ; Knight, Sean LU ; Bulancea-Lindvall, Oscar ; Mu, Sai ; Kühne, Philipp ; Stokey, Megan ; Ruder, Alexander ; Rindert, Viktor LU orcid ; Ivády, Viktor and Abrikosov, Igor A. , et al. (2024) In Physical Review B 109(21).
Abstract

We demonstrate detection and measurement of electron paramagnetic spin resonances (EPR) of iron defects in β-Ga2O3 utilizing generalized ellipsometry at frequencies between 110 and 170 GHz. The experiments are performed on an Fe-doped single crystal in a free-beam configuration in reflection at 45∘ and magnetic fields between 3 and 7 T. In contrast with low-field, low-frequency EPR measurements, we observe all five transitions of the s=5/2 high-spin state Fe3+ simultaneously. We confirm that ferric Fe3+ is predominantly found at octahedrally coordinated Ga sites. We obtain the full set of fourth-order monoclinic zero-field splitting parameters for both octahedrally and tetrahedrally coordinated sites by employing measurements at... (More)

We demonstrate detection and measurement of electron paramagnetic spin resonances (EPR) of iron defects in β-Ga2O3 utilizing generalized ellipsometry at frequencies between 110 and 170 GHz. The experiments are performed on an Fe-doped single crystal in a free-beam configuration in reflection at 45∘ and magnetic fields between 3 and 7 T. In contrast with low-field, low-frequency EPR measurements, we observe all five transitions of the s=5/2 high-spin state Fe3+ simultaneously. We confirm that ferric Fe3+ is predominantly found at octahedrally coordinated Ga sites. We obtain the full set of fourth-order monoclinic zero-field splitting parameters for both octahedrally and tetrahedrally coordinated sites by employing measurements at multiple sample azimuth rotations. The capability of high-field EPR allows us to demonstrate that simplified second-order orthorhombic spin Hamiltonians are insufficient, and fourth-order terms as well as consideration of the monoclinic symmetry are needed. These findings are supported by computational approaches based on density-functional theory for second-order and on ligand-field theory for fourth-order parameters of the spin Hamiltonian. Terahertz ellipsometry is a way to measure spin resonances in a cavity-free setup. Its possibility of varying the probe frequency arbitrarily without otherwise changing the experimental setup offers unique means of truly disentangling different components of highly anisotropic spin Hamiltonians.

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publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B
volume
109
issue
21
article number
214106
pages
13 pages
publisher
American Physical Society
external identifiers
  • scopus:85196417819
ISSN
2469-9950
DOI
10.1103/PhysRevB.109.214106
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by "https://www.kb.se/samverkan-och-utveckling/oppen-tillgang-och-bibsamkonsortiet/bibsamkonsortiet.html"Bibsam.
id
ebf997f5-33ff-4bba-8e03-358b8a157f90
date added to LUP
2024-08-07 16:57:13
date last changed
2024-08-13 16:40:55
@article{ebf997f5-33ff-4bba-8e03-358b8a157f90,
  abstract     = {{<p>We demonstrate detection and measurement of electron paramagnetic spin resonances (EPR) of iron defects in β-Ga2O3 utilizing generalized ellipsometry at frequencies between 110 and 170 GHz. The experiments are performed on an Fe-doped single crystal in a free-beam configuration in reflection at 45∘ and magnetic fields between 3 and 7 T. In contrast with low-field, low-frequency EPR measurements, we observe all five transitions of the s=5/2 high-spin state Fe3+ simultaneously. We confirm that ferric Fe3+ is predominantly found at octahedrally coordinated Ga sites. We obtain the full set of fourth-order monoclinic zero-field splitting parameters for both octahedrally and tetrahedrally coordinated sites by employing measurements at multiple sample azimuth rotations. The capability of high-field EPR allows us to demonstrate that simplified second-order orthorhombic spin Hamiltonians are insufficient, and fourth-order terms as well as consideration of the monoclinic symmetry are needed. These findings are supported by computational approaches based on density-functional theory for second-order and on ligand-field theory for fourth-order parameters of the spin Hamiltonian. Terahertz ellipsometry is a way to measure spin resonances in a cavity-free setup. Its possibility of varying the probe frequency arbitrarily without otherwise changing the experimental setup offers unique means of truly disentangling different components of highly anisotropic spin Hamiltonians.</p>}},
  author       = {{Richter, Steffen and Knight, Sean and Bulancea-Lindvall, Oscar and Mu, Sai and Kühne, Philipp and Stokey, Megan and Ruder, Alexander and Rindert, Viktor and Ivády, Viktor and Abrikosov, Igor A. and Van De Walle, Chris G. and Schubert, Mathias and Darakchieva, Vanya}},
  issn         = {{2469-9950}},
  language     = {{eng}},
  month        = {{06}},
  number       = {{21}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review B}},
  title        = {{High-field/high-frequency electron spin resonances of Fe-doped β-Ga2 O3 by terahertz generalized ellipsometry : Monoclinic symmetry effects}},
  url          = {{http://dx.doi.org/10.1103/PhysRevB.109.214106}},
  doi          = {{10.1103/PhysRevB.109.214106}},
  volume       = {{109}},
  year         = {{2024}},
}