Low-spin ground state of the giant single-molecule magnets {Mn70} and {Mn84}

authored by: Roman Rausch, Christoph Karrasch
Abstract: The single-molecule magnets {Mn70} and {Mn84} are characterized by a 14-site unit cell with S=2 spin sites arranged in a circular geometry. Experimentally, these systems exhibit a magnetic ground state with a notably low total spin Stot=5-7. Up to now, this low-spin ground state has been up difficult to describe theoretically due to the complexity of the quantum Heisenberg model for such a large system. In this paper, we fill this gap and demonstrate that the ground state of {Mn70} and {Mn84} is in fact governed by a small, finite Stot in quantitative agreement with the experiment. We employ accurate, large-scale SU(2)-symmetric density-matrix renormalization group calculations for a quantum Heisenberg model with previously published exchange parameters obtained by density-functional theory. We do not find a low-spin state for the same parameters and S=1 and thus propose that frustrated systems with S≥2 are inherently prone to weak ferromagnetic interactions. This could account for the prevalence of similar low-spin Mn-based single-molecule magnets. Finally, we compute the full magnetization curve and find wide plateaus at 10/14, 11/14, 12/14, and 13/14 of the saturation, which can be traced back to nearly independent three-site clusters with broken intercluster bonds.
External Organisation(s): Technische Universität Braunschweig
Type: Article
Journal: Physical Review B
Volume: 111
ISSN: 2469-9950
Publication date: 19.02.2025
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Electronic, Optical and Magnetic Materials, Condensed Matter Physics
Electronic version(s): https://doi.org/10.1103/PhysRevB.111.075143 (Access: Open)

BibTeX

@article{d6136714059d48d59c914ae87e89653e,
title = "Low-spin ground state of the giant single-molecule magnets {Mn70} and {Mn84}",
abstract = "The single-molecule magnets {Mn70} and {Mn84} are characterized by a 14-site unit cell with S=2 spin sites arranged in a circular geometry. Experimentally, these systems exhibit a magnetic ground state with a notably low total spin Stot=5-7. Up to now, this low-spin ground state has been up difficult to describe theoretically due to the complexity of the quantum Heisenberg model for such a large system. In this paper, we fill this gap and demonstrate that the ground state of {Mn70} and {Mn84} is in fact governed by a small, finite Stot in quantitative agreement with the experiment. We employ accurate, large-scale SU(2)-symmetric density-matrix renormalization group calculations for a quantum Heisenberg model with previously published exchange parameters obtained by density-functional theory. We do not find a low-spin state for the same parameters and S=1 and thus propose that frustrated systems with S≥2 are inherently prone to weak ferromagnetic interactions. This could account for the prevalence of similar low-spin Mn-based single-molecule magnets. Finally, we compute the full magnetization curve and find wide plateaus at 10/14, 11/14, 12/14, and 13/14 of the saturation, which can be traced back to nearly independent three-site clusters with broken intercluster bonds.",
author = "Roman Rausch and Christoph Karrasch",
note = "Publisher Copyright: {\textcopyright} 2025 authors. Published by the American Physical Society.",
year = "2025",
month = feb,
day = "19",
doi = "10.1103/PhysRevB.111.075143",
language = "English",
volume = "111",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Institute of Physics",
number = "7",
}