Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb2@C79N
(2022) In Nanoscale 14(27). p.9877-9892- Abstract
Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb2@C79N, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb2@C79N exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.5-4 T. Monolayers of Tb2@C79N were deposited onto Cu(111) and Au(111) by evaporation in ultra-high vacuum conditions, and their... (More)
Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb2@C79N, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb2@C79N exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.5-4 T. Monolayers of Tb2@C79N were deposited onto Cu(111) and Au(111) by evaporation in ultra-high vacuum conditions, and their topography and electronic structure were characterized by scanning tunneling microscopy and spectroscopy (STM/STS). X-ray photoelectron spectroscopy (XPS), in combination with DFT studies, revealed that the nitrogen atom of the azafullerene cage tends to avoid metallic surfaces. Magnetic properties of the (sub)monolayers were then studied by X-ray magnetic circular dichroism (XMCD) at the Tb-M4,5 absorption edge. While in bulk powder samples Tb2@C79N behaves as a single-molecule magnet with ferromagnetically coupled magnetic moments and blocking of magnetization at 28 K, its monolayers exhibited a different ground state with antiferromagnetic coupling of Tb magnetic moments. To understand if this unexpected behavior is caused by a strong hybridization of fullerenes with metallic substrates, XMCD measurements were also performed for Tb2@C79N adsorbed on h-BN|Rh(111) and MgO|Ag(100). The co-existence of two forms of Tb2@C79N was found on these substrates as well, but magnetization curves showed narrow magnetic hysteresis detectable up to 25 K. The non-magnetic state of Tb2@C79N in monolayers is assigned to anionic Tb2@C79N− species with doubly-occupied Tb-Tb bonding orbital and antiferromagnetic coupling of the Tb moments. A charge transfer from the substrate or trapping of secondary electrons are discussed as a plausible origin of these species.
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- author
- organization
- publishing date
- 2022-06-28
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Nanoscale
- volume
- 14
- issue
- 27
- pages
- 16 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- pmid:35781298
- scopus:85133965516
- ISSN
- 2040-3364
- DOI
- 10.1039/d1nr08475e
- language
- English
- LU publication?
- yes
- id
- bb15e419-9f40-46e2-8ef6-e041f8505f90
- date added to LUP
- 2022-10-10 11:08:54
- date last changed
- 2024-06-13 12:38:24
@article{bb15e419-9f40-46e2-8ef6-e041f8505f90,
abstract = {{<p>Realization of stable spin states in surface-supported magnetic molecules is crucial for their applications in molecular spintronics, memory storage or quantum information processing. In this work, we studied the surface magnetism of dimetallo-azafullerene Tb<sub>2</sub>@C<sub>79</sub>N, showing a broad magnetic hysteresis in a bulk form. Surprisingly, monolayers of Tb<sub>2</sub>@C<sub>79</sub>N exhibited a completely different behavior, with the prevalence of a ground state with antiferromagnetic coupling at low magnetic field and a metamagnetic transition in the magnetic field of 2.5-4 T. Monolayers of Tb<sub>2</sub>@C<sub>79</sub>N were deposited onto Cu(111) and Au(111) by evaporation in ultra-high vacuum conditions, and their topography and electronic structure were characterized by scanning tunneling microscopy and spectroscopy (STM/STS). X-ray photoelectron spectroscopy (XPS), in combination with DFT studies, revealed that the nitrogen atom of the azafullerene cage tends to avoid metallic surfaces. Magnetic properties of the (sub)monolayers were then studied by X-ray magnetic circular dichroism (XMCD) at the Tb-M<sub>4,5</sub> absorption edge. While in bulk powder samples Tb<sub>2</sub>@C<sub>79</sub>N behaves as a single-molecule magnet with ferromagnetically coupled magnetic moments and blocking of magnetization at 28 K, its monolayers exhibited a different ground state with antiferromagnetic coupling of Tb magnetic moments. To understand if this unexpected behavior is caused by a strong hybridization of fullerenes with metallic substrates, XMCD measurements were also performed for Tb<sub>2</sub>@C<sub>79</sub>N adsorbed on h-BN|Rh(111) and MgO|Ag(100). The co-existence of two forms of Tb<sub>2</sub>@C<sub>79</sub>N was found on these substrates as well, but magnetization curves showed narrow magnetic hysteresis detectable up to 25 K. The non-magnetic state of Tb<sub>2</sub>@C<sub>79</sub>N in monolayers is assigned to anionic Tb<sub>2</sub>@C<sub>79</sub>N<sup>−</sup> species with doubly-occupied Tb-Tb bonding orbital and antiferromagnetic coupling of the Tb moments. A charge transfer from the substrate or trapping of secondary electrons are discussed as a plausible origin of these species.</p>}},
author = {{Koutsouflakis, Emmanouil and Krylov, Denis and Bachellier, Nicolas and Sostina, Daria and Dubrovin, Vasilii and Liu, Fupin and Spree, Lukas and Velkos, Georgios and Schimmel, Sebastian and Wang, Yaofeng and Büchner, Bernd and Westerström, Rasmus and Bulbucan, Claudiu and Kirkpatrick, Kyle and Muntwiler, Matthias and Dreiser, Jan and Greber, Thomas and Avdoshenko, Stas M. and Dorn, Harry and Popov, Alexey A.}},
issn = {{2040-3364}},
language = {{eng}},
month = {{06}},
number = {{27}},
pages = {{9877--9892}},
publisher = {{Royal Society of Chemistry}},
series = {{Nanoscale}},
title = {{Metamagnetic transition and a loss of magnetic hysteresis caused by electron trapping in monolayers of single-molecule magnet Tb<sub>2</sub>@C<sub>79</sub>N}},
url = {{http://dx.doi.org/10.1039/d1nr08475e}},
doi = {{10.1039/d1nr08475e}},
volume = {{14}},
year = {{2022}},
}