Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C2O4)2⋅xH2O

Aly H. Abdeldaim; Teng Li; Lewis Farrar; Alexander A. Tsirlin; Wenjiao Yao; Alexandra S. Gibbs; Pascal Manuel; Philip Lightfoot; Gøran J. Nilsen; Lucy Clark

doi:10.1103/PhysRevMaterials.4.104414

Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C₂O₄)₂⋅xH₂O

Aly H. Abdeldaim, Teng Li, Lewis Farrar, Alexander A. Tsirlin, Wenjiao Yao, Alexandra S. Gibbs, Pascal Manuel, Philip Lightfoot, Gøran J. Nilsen, Lucy Clark^*

^*Corresponding author for this work

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Abstract

We report the crystal structures and magnetic properties of two pseudopolymorphs of the S=1/2 Ti³⁺ coordination framework, KTi(C₂O₄)₂⋅xH₂O. Single-crystal x-ray and powder neutron diffraction measurements on α−KTi(C₂O₄)₂⋅xH₂O confirm its structure in the tetragonal I4/mcm space group with a square planar arrangement of Ti³⁺ ions. Magnetometry and specific heat measurements reveal weak antiferromagnetic interactions, with J₁≈7 K and J₂/J₁=0.11 indicating a slight frustration of nearest- and next-nearest-neighbor interactions. Below 1.8 K, α−KTi(C₂O₄)₂⋅xH₂O undergoes a transition to G-type antiferromagnetic order with magnetic moments aligned along the c axis of the tetragonal structure. The estimated ordered moment of Ti³⁺ in α−KTi(C₂O₄)₂⋅xH₂O is suppressed from its spin-only value to 0.62(3) μ_B, thus verifying the two-dimensional nature of the magnetic interactions within the system. β−KTi(C₂O₄)₂⋅2H₂O, on the other hand, realizes a three-dimensional diamondlike magnetic network of Ti³⁺ moments within a hexagonal P6₂22 structure. An antiferromagnetic exchange coupling of J≈54 K—an order of magnitude larger than in α−KTi(C₂O₄)₂⋅xH₂O—is extracted from magnetometry and specific heat data. β−KTi(C2O4)2⋅2H2O undergoes Néel ordering at TN=28 K, with the magnetic moments aligned within the ab plane and a slightly reduced ordered moment of 0.79 μ_B per Ti³⁺. Through density-functional theory calculations, we address the origin of the large difference in the exchange parameters between the α and β pseudopolymorphs. Given their observed magnetic behaviors, we propose α−KTi(C₂O₄)₂⋅xH₂O and β−KTi(C₂O₄)₂⋅2H₂O as close to ideal model S =1/2 Heisenberg square and diamond lattice antiferromagnets, respectively.

Original language	English
Article number	104414
Number of pages	12
Journal	Physical Review Materials
Volume	4
Issue number	10
DOIs	https://doi.org/10.1103/PhysRevMaterials.4.104414
Publication status	Published - 23 Oct 2020

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Abdeldaim, A. H., Li, T., Farrar, L., Tsirlin, A. A., Yao, W., Gibbs, A. S., Manuel, P., Lightfoot, P., Nilsen, G. J., & Clark, L. (2020). Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C₂O₄)₂⋅xH₂O. Physical Review Materials, 4(10), Article 104414. https://doi.org/10.1103/PhysRevMaterials.4.104414

@article{2768359f12a443f89a3df0233f67c05d,

title = "Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C2O4)2⋅xH2O",

abstract = "We report the crystal structures and magnetic properties of two pseudopolymorphs of the S=1/2 Ti3+ coordination framework, KTi(C2O4)2⋅xH2O. Single-crystal x-ray and powder neutron diffraction measurements on α−KTi(C2O4)2⋅xH2O confirm its structure in the tetragonal I4/mcm space group with a square planar arrangement of Ti3+ ions. Magnetometry and specific heat measurements reveal weak antiferromagnetic interactions, with J1≈7 K and J2/J1=0.11 indicating a slight frustration of nearest- and next-nearest-neighbor interactions. Below 1.8 K, α−KTi(C2O4)2⋅xH2O undergoes a transition to G-type antiferromagnetic order with magnetic moments aligned along the c axis of the tetragonal structure. The estimated ordered moment of Ti3+ in α−KTi(C2O4)2⋅xH2O is suppressed from its spin-only value to 0.62(3) μB, thus verifying the two-dimensional nature of the magnetic interactions within the system. β−KTi(C2O4)2⋅2H2O, on the other hand, realizes a three-dimensional diamondlike magnetic network of Ti3+ moments within a hexagonal P6222 structure. An antiferromagnetic exchange coupling of J≈54 K—an order of magnitude larger than in α−KTi(C2O4)2⋅xH2O—is extracted from magnetometry and specific heat data. β−KTi(C2O4)2⋅2H2O undergoes N{\'e}el ordering at TN=28 K, with the magnetic moments aligned within the ab plane and a slightly reduced ordered moment of 0.79 μB per Ti3+. Through density-functional theory calculations, we address the origin of the large difference in the exchange parameters between the α and β pseudopolymorphs. Given their observed magnetic behaviors, we propose α−KTi(C2O4)2⋅xH2O and β−KTi(C2O4)2⋅2H2O as close to ideal model S =1/2 Heisenberg square and diamond lattice antiferromagnets, respectively.",

author = "Abdeldaim, {Aly H.} and Teng Li and Lewis Farrar and Tsirlin, {Alexander A.} and Wenjiao Yao and Gibbs, {Alexandra S.} and Pascal Manuel and Philip Lightfoot and Nilsen, {G{\o}ran J.} and Lucy Clark",

note = "Provision of a PhD studentship to A.H.A. by the University of Liverpool and the Science and Technology Facilities Council (STFC) is gratefully acknowledged. The work of T.L. was funded by the University of St Andrews and China Scholarship Council (CSC) joint scholarship (201606280032). A.T. was funded by the Federal Ministry of Education and Research through the Sofja Kovalevskaya Award of Alexander von Humboldt Foundation. Work at St Andrews was supported by the Leverhulme Trust (RPG-2013-343).",

year = "2020",

month = oct,

day = "23",

doi = "10.1103/PhysRevMaterials.4.104414",

language = "English",

volume = "4",

journal = "Physical Review Materials",

issn = "2475-9953",

publisher = "American Physical Society",

number = "10",

}

Abdeldaim, AH, Li, T, Farrar, L, Tsirlin, AA, Yao, W, Gibbs, AS, Manuel, P, Lightfoot, P, Nilsen, GJ & Clark, L 2020, 'Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C₂O₄)₂⋅xH₂O', Physical Review Materials, vol. 4, no. 10, 104414. https://doi.org/10.1103/PhysRevMaterials.4.104414

TY - JOUR

T1 - Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C2O4)2⋅xH2O

AU - Abdeldaim, Aly H.

AU - Li, Teng

AU - Farrar, Lewis

AU - Tsirlin, Alexander A.

AU - Yao, Wenjiao

AU - Gibbs, Alexandra S.

AU - Manuel, Pascal

AU - Lightfoot, Philip

AU - Nilsen, Gøran J.

AU - Clark, Lucy

N1 - Provision of a PhD studentship to A.H.A. by the University of Liverpool and the Science and Technology Facilities Council (STFC) is gratefully acknowledged. The work of T.L. was funded by the University of St Andrews and China Scholarship Council (CSC) joint scholarship (201606280032). A.T. was funded by the Federal Ministry of Education and Research through the Sofja Kovalevskaya Award of Alexander von Humboldt Foundation. Work at St Andrews was supported by the Leverhulme Trust (RPG-2013-343).

PY - 2020/10/23

Y1 - 2020/10/23

N2 - We report the crystal structures and magnetic properties of two pseudopolymorphs of the S=1/2 Ti3+ coordination framework, KTi(C2O4)2⋅xH2O. Single-crystal x-ray and powder neutron diffraction measurements on α−KTi(C2O4)2⋅xH2O confirm its structure in the tetragonal I4/mcm space group with a square planar arrangement of Ti3+ ions. Magnetometry and specific heat measurements reveal weak antiferromagnetic interactions, with J1≈7 K and J2/J1=0.11 indicating a slight frustration of nearest- and next-nearest-neighbor interactions. Below 1.8 K, α−KTi(C2O4)2⋅xH2O undergoes a transition to G-type antiferromagnetic order with magnetic moments aligned along the c axis of the tetragonal structure. The estimated ordered moment of Ti3+ in α−KTi(C2O4)2⋅xH2O is suppressed from its spin-only value to 0.62(3) μB, thus verifying the two-dimensional nature of the magnetic interactions within the system. β−KTi(C2O4)2⋅2H2O, on the other hand, realizes a three-dimensional diamondlike magnetic network of Ti3+ moments within a hexagonal P6222 structure. An antiferromagnetic exchange coupling of J≈54 K—an order of magnitude larger than in α−KTi(C2O4)2⋅xH2O—is extracted from magnetometry and specific heat data. β−KTi(C2O4)2⋅2H2O undergoes Néel ordering at TN=28 K, with the magnetic moments aligned within the ab plane and a slightly reduced ordered moment of 0.79 μB per Ti3+. Through density-functional theory calculations, we address the origin of the large difference in the exchange parameters between the α and β pseudopolymorphs. Given their observed magnetic behaviors, we propose α−KTi(C2O4)2⋅xH2O and β−KTi(C2O4)2⋅2H2O as close to ideal model S =1/2 Heisenberg square and diamond lattice antiferromagnets, respectively.

AB - We report the crystal structures and magnetic properties of two pseudopolymorphs of the S=1/2 Ti3+ coordination framework, KTi(C2O4)2⋅xH2O. Single-crystal x-ray and powder neutron diffraction measurements on α−KTi(C2O4)2⋅xH2O confirm its structure in the tetragonal I4/mcm space group with a square planar arrangement of Ti3+ ions. Magnetometry and specific heat measurements reveal weak antiferromagnetic interactions, with J1≈7 K and J2/J1=0.11 indicating a slight frustration of nearest- and next-nearest-neighbor interactions. Below 1.8 K, α−KTi(C2O4)2⋅xH2O undergoes a transition to G-type antiferromagnetic order with magnetic moments aligned along the c axis of the tetragonal structure. The estimated ordered moment of Ti3+ in α−KTi(C2O4)2⋅xH2O is suppressed from its spin-only value to 0.62(3) μB, thus verifying the two-dimensional nature of the magnetic interactions within the system. β−KTi(C2O4)2⋅2H2O, on the other hand, realizes a three-dimensional diamondlike magnetic network of Ti3+ moments within a hexagonal P6222 structure. An antiferromagnetic exchange coupling of J≈54 K—an order of magnitude larger than in α−KTi(C2O4)2⋅xH2O—is extracted from magnetometry and specific heat data. β−KTi(C2O4)2⋅2H2O undergoes Néel ordering at TN=28 K, with the magnetic moments aligned within the ab plane and a slightly reduced ordered moment of 0.79 μB per Ti3+. Through density-functional theory calculations, we address the origin of the large difference in the exchange parameters between the α and β pseudopolymorphs. Given their observed magnetic behaviors, we propose α−KTi(C2O4)2⋅xH2O and β−KTi(C2O4)2⋅2H2O as close to ideal model S =1/2 Heisenberg square and diamond lattice antiferromagnets, respectively.

U2 - 10.1103/PhysRevMaterials.4.104414

DO - 10.1103/PhysRevMaterials.4.104414

M3 - Article

AN - SCOPUS:85095433240

SN - 2475-9953

VL - 4

JO - Physical Review Materials

JF - Physical Review Materials

IS - 10

M1 - 104414

ER -

Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C2O4)2⋅xH2O

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Quantum Spin Liquids: New Chemical Paradigms in the Search for Quantum Spin Liquids

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Realizing square and diamond lattice S =1/2 Heisenberg antiferromagnet models in the α and β phases of the coordination framework, KTi(C₂O₄)₂⋅xH₂O