Observation of Unprecedented Fractional Magnetization Plateaus in a New Shastry-Sutherland Ising Compound

Lalit Yadav; Afonso Rufino; Rabindranath Bag; Matthew Ennis; Jan Alexander Koziol; Clarina Dela Cruz; Alexander I. Kolesnikov; V. Ovidiu Garlea; Keith M. Taddei; David Graf; Kai Phillip Schmidt; Frédéric Mila; Sara Haravifard

doi:10.1103/9ynf-xx1t

Observation of Unprecedented Fractional Magnetization Plateaus in a New Shastry-Sutherland Ising Compound

Lalit Yadav
, Afonso Rufino
, Rabindranath Bag
, Matthew Ennis
, Jan Alexander Koziol
, Clarina Dela Cruz
, Alexander I. Kolesnikov
, V. Ovidiu Garlea
, Keith M. Taddei
, David Graf
, Kai Phillip Schmidt
, Frédéric Mila
, Sara Haravifard

Direct Geometry

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

3 Scopus citations

Abstract

Geometrically frustrated magnetic systems, such as those based on the Shastry-Sutherland lattice (SSL), offer a rich playground for exploring unconventional magnetic states. The delicate balance between competing interactions in these systems leads to the emergence of novel phases. We present the characterization of Er2Be2GeO7, an SSL compound with Er3+ ions forming orthogonal dimers separated by nonmagnetic layers whose structure is invariant under the P4¯21m space group. Neutron scattering reveals an antiferromagnetic dimer structure at zero field, typical of Ising spins on that lattice and consistent with the anisotropic magnetization observed. However, magnetization measurements exhibit fractional plateaus at 1/4 and 1/2 of saturation, in contrast to the expected 1/3 plateau of the SSL Ising model. By comparing the energy of candidate states with ground-state lower bounds we show that this behavior requires spatially anisotropic interactions, leading to an anisotropic Shastry-Sutherland Ising model symmetric under the Cmm2 space group. This anisotropy is consistent with the small orthorhombic distortion observed with single-crystal neutron diffraction. The other properties, including thermodynamics, which have been investigated theoretically using tensor networks, point to small residual interactions, potentially due to further couplings and quantum fluctuations. This study highlights Er2Be2GeO7 as a promising platform for investigating exotic magnetic phenomena.

Original language	English
Article number	041045
Journal	Physical Review X
Volume	15
Issue number	4
DOIs	https://doi.org/10.1103/9ynf-xx1t
State	Published - Oct 2025

Funding

The research performed at Duke University was supported by NSF Award No. DMR-2327555. A portion of this research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-2128556 and the State of Florida. The research performed at E. P. F. L. has been supported by the Swiss National Science Foundation Grant No. 212082. The research performed at F. A. U. was supported by the Munich Quantum Valley, which is supported by the Bavarian state government with funds from the Hightech Agenda Bayern Plus. For the numerical calculations of the unit-cell-based ground-state search, we acknowledge the scientific support and HPC resources provided by the Erlangen National High Performance Computing Center (NHR@FAU) of the Friedrich-Alexander-Universität Erlangen-Nürnberg. The research performed at Duke University was supported by NSF Award No. DMR-2327555. A portion of this research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement No. DMR-2128556 and the State of Florida. The research performed at E.P.F.L. has been supported by the Swiss National Science Foundation Grant No. 212082. The research performed at F.A.U. was supported by the Munich Quantum Valley, which is supported by the Bavarian state government with funds from the Hightech Agenda Bayern Plus. For the numerical calculations of the unit-cell-based ground-state search, we acknowledge the scientific support and HPC resources provided by the Erlangen National High Performance Computing Center (NHR@FAU) of the Friedrich-Alexander-Universitet Erlangen-Nurnberg.

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title = "Observation of Unprecedented Fractional Magnetization Plateaus in a New Shastry-Sutherland Ising Compound",

abstract = "Geometrically frustrated magnetic systems, such as those based on the Shastry-Sutherland lattice (SSL), offer a rich playground for exploring unconventional magnetic states. The delicate balance between competing interactions in these systems leads to the emergence of novel phases. We present the characterization of Er2Be2GeO7, an SSL compound with Er3+ ions forming orthogonal dimers separated by nonmagnetic layers whose structure is invariant under the P4¯21m space group. Neutron scattering reveals an antiferromagnetic dimer structure at zero field, typical of Ising spins on that lattice and consistent with the anisotropic magnetization observed. However, magnetization measurements exhibit fractional plateaus at 1/4 and 1/2 of saturation, in contrast to the expected 1/3 plateau of the SSL Ising model. By comparing the energy of candidate states with ground-state lower bounds we show that this behavior requires spatially anisotropic interactions, leading to an anisotropic Shastry-Sutherland Ising model symmetric under the Cmm2 space group. This anisotropy is consistent with the small orthorhombic distortion observed with single-crystal neutron diffraction. The other properties, including thermodynamics, which have been investigated theoretically using tensor networks, point to small residual interactions, potentially due to further couplings and quantum fluctuations. This study highlights Er2Be2GeO7 as a promising platform for investigating exotic magnetic phenomena.",

author = "Lalit Yadav and Afonso Rufino and Rabindranath Bag and Matthew Ennis and Koziol, \{Jan Alexander\} and Cruz, \{Clarina Dela\} and Kolesnikov, \{Alexander I.\} and Garlea, \{V. Ovidiu\} and Taddei, \{Keith M.\} and David Graf and Schmidt, \{Kai Phillip\} and Fr{\'e}d{\'e}ric Mila and Sara Haravifard",

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AU - Yadav, Lalit

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AU - Bag, Rabindranath

AU - Ennis, Matthew

AU - Koziol, Jan Alexander

AU - Cruz, Clarina Dela

AU - Kolesnikov, Alexander I.

AU - Garlea, V. Ovidiu

AU - Taddei, Keith M.

AU - Graf, David

AU - Schmidt, Kai Phillip

AU - Mila, Frédéric

AU - Haravifard, Sara

N1 - Publisher Copyright: © 2025 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.

PY - 2025/10

Y1 - 2025/10

N2 - Geometrically frustrated magnetic systems, such as those based on the Shastry-Sutherland lattice (SSL), offer a rich playground for exploring unconventional magnetic states. The delicate balance between competing interactions in these systems leads to the emergence of novel phases. We present the characterization of Er2Be2GeO7, an SSL compound with Er3+ ions forming orthogonal dimers separated by nonmagnetic layers whose structure is invariant under the P4¯21m space group. Neutron scattering reveals an antiferromagnetic dimer structure at zero field, typical of Ising spins on that lattice and consistent with the anisotropic magnetization observed. However, magnetization measurements exhibit fractional plateaus at 1/4 and 1/2 of saturation, in contrast to the expected 1/3 plateau of the SSL Ising model. By comparing the energy of candidate states with ground-state lower bounds we show that this behavior requires spatially anisotropic interactions, leading to an anisotropic Shastry-Sutherland Ising model symmetric under the Cmm2 space group. This anisotropy is consistent with the small orthorhombic distortion observed with single-crystal neutron diffraction. The other properties, including thermodynamics, which have been investigated theoretically using tensor networks, point to small residual interactions, potentially due to further couplings and quantum fluctuations. This study highlights Er2Be2GeO7 as a promising platform for investigating exotic magnetic phenomena.

AB - Geometrically frustrated magnetic systems, such as those based on the Shastry-Sutherland lattice (SSL), offer a rich playground for exploring unconventional magnetic states. The delicate balance between competing interactions in these systems leads to the emergence of novel phases. We present the characterization of Er2Be2GeO7, an SSL compound with Er3+ ions forming orthogonal dimers separated by nonmagnetic layers whose structure is invariant under the P4¯21m space group. Neutron scattering reveals an antiferromagnetic dimer structure at zero field, typical of Ising spins on that lattice and consistent with the anisotropic magnetization observed. However, magnetization measurements exhibit fractional plateaus at 1/4 and 1/2 of saturation, in contrast to the expected 1/3 plateau of the SSL Ising model. By comparing the energy of candidate states with ground-state lower bounds we show that this behavior requires spatially anisotropic interactions, leading to an anisotropic Shastry-Sutherland Ising model symmetric under the Cmm2 space group. This anisotropy is consistent with the small orthorhombic distortion observed with single-crystal neutron diffraction. The other properties, including thermodynamics, which have been investigated theoretically using tensor networks, point to small residual interactions, potentially due to further couplings and quantum fluctuations. This study highlights Er2Be2GeO7 as a promising platform for investigating exotic magnetic phenomena.

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ER -

Observation of Unprecedented Fractional Magnetization Plateaus in a New Shastry-Sutherland Ising Compound

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