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Precise measurement of angles between two magnetic moments and their configurational stability in single-molecule magnets


Westerström, Rasmus; Dubrovin, Vasilii; Junghans, Katrin; Schlesier, Christin; Büchner, Bernd; Avdoshenko, Stanislav M; Popov, Alexey A; Kostanyan, Aram; Dreiser, Jan; Greber, Thomas (2021). Precise measurement of angles between two magnetic moments and their configurational stability in single-molecule magnets. Physical review B, 104(22):224401.

Abstract

A key parameter for the low-temperature magnetic coupling of in dinuclear lanthanide single-molecule magnets (SMMs) is the barrier UFA resulting from the exchange and dipole interactions between the two 4f moments. Here we extend the pseudospin model previously used to describe the ground state of dinuclear endofullerenes to account for variations in the orientation of the single-ion anisotropy axes and apply it to the two SMMs Dy2ScN@C80 and Dy2TiC@C80. While x-ray magnetic circular dichroism (XMCD) indicates the same Jz=15/2 Dy ground state in both molecules, the Dy-Dy coupling strength and the stability of magnetization is distinct. We demonstrate that both the magnitude of the barrier UFA and the angle between the two 4f moments are determined directly from precise temperature-dependent magnetization data to an accuracy better than 1∘. The experimentally found angles between the 4f moments are in excellent agreement with calculated angles between the quantization axes of the two Dy ions. Theory indicates a larger deviation of the orientation of the Dy magnetic moments from the Dy bond axes to the central ion in Dy2TiC@C80. This may explain the lower stability of the magnetization in Dy2TiC@C80, although it exhibits a ∼49% stronger exchange coupling than in Dy2ScN@C80.

Abstract

A key parameter for the low-temperature magnetic coupling of in dinuclear lanthanide single-molecule magnets (SMMs) is the barrier UFA resulting from the exchange and dipole interactions between the two 4f moments. Here we extend the pseudospin model previously used to describe the ground state of dinuclear endofullerenes to account for variations in the orientation of the single-ion anisotropy axes and apply it to the two SMMs Dy2ScN@C80 and Dy2TiC@C80. While x-ray magnetic circular dichroism (XMCD) indicates the same Jz=15/2 Dy ground state in both molecules, the Dy-Dy coupling strength and the stability of magnetization is distinct. We demonstrate that both the magnitude of the barrier UFA and the angle between the two 4f moments are determined directly from precise temperature-dependent magnetization data to an accuracy better than 1∘. The experimentally found angles between the 4f moments are in excellent agreement with calculated angles between the quantization axes of the two Dy ions. Theory indicates a larger deviation of the orientation of the Dy magnetic moments from the Dy bond axes to the central ion in Dy2TiC@C80. This may explain the lower stability of the magnetization in Dy2TiC@C80, although it exhibits a ∼49% stronger exchange coupling than in Dy2ScN@C80.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Electronic, Optical and Magnetic Materials
Physical Sciences > Condensed Matter Physics
Language:English
Date:1 December 2021
Deposited On:06 Jan 2022 05:07
Last Modified:28 Jan 2024 02:38
Publisher:American Physical Society
ISSN:2469-9950
OA Status:Green
Publisher DOI:https://doi.org/10.1103/physrevb.104.224401
  • Content: Published Version
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)