Room-temperature structural phase transition in the quasi-2D spin-
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 Heisenberg antiferromagnet 
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow><mml:mi>Cu</mml:mi><mml:mo>(</mml:mo><mml:mi>pz</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>ClO</mml:mi><mml:mn>4</mml:mn>

Barbero, Nicolò; Medarde, M.; Shang, T.; Sheptyakov, Denis; Landee, Christopher P.; Mesot, J.; Ott, H. R.; Shiroka, T.

doi:10.1103/physrevmaterials.3.053602

Cited by 3 publications

(4 citation statements)

References 26 publications

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“…However, the pyrazine bond lengths in the other compounds studied here (especially 1, which displays large differences in the inplain nearest-neighbor interactions) differ by, at most, 0.001 Å, so this mechanism seems unlikely. Moreover, the experimental magnetic behavior of 4 has been shown to be only marginally affected by a shift in the orientations of the pyrazine rings and the ClO -4 counterions [17].…”

Section: Introductionmentioning

confidence: 99%

“…The exchange interactions in structurally homologous, chemically similar, materials can often vary widely [11,12], offering an opportunity to design and investigate materials via finely tuning their geometries. Although an abundance of experimental information is available for these materials [9,10,[12][13][14][15][16][17][18][19], the factors that control the magnetic interactions are still debated. To be able to design materials with specific sets of magnetic interactions, these factors need to be understood in great detail.…”

Section: Introductionmentioning

confidence: 99%

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The princess and the pea: on the outsized role of inter-layer ligands in copper-pyrazine antiferromagnets

Kenny,

Jacko,

Powell

2021

Preprint

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We investigate the cause of exchange anisotropy in a family of copper-based, quasi-twodimensional materials with very similar geometries. This family differs mainly in the inter-layer separation, but have very different magnetic interactions even within the basal plane. We use density functional theory and Wannier functions to parameterize two complimentary tight-binding models and show that the superexchange between the Cu 2+ ions is dominated by a through-space interaction between hybrid Cu-pyrazine orbitals centered on the copper atoms. We find no correlations between the strength of this exchange interaction with homologous geometric features across the compounds, such as Cu and pyrazine bond lengths and orientations of nearby counter-ions. We find that the pyrazine tilt angles do not affect the Cu-pyrazine-Cu exchange because the lowest unoccupied molecular orbital on the pyrazine is at a very high energy (relative to the frontier orbitals, which are Cu-based). We conclude that the anisotropy of magnetic interactions within this family of materials is largely unpredictable before the crystal structure is firmly established -it is due to non-homologous geometric features such as the inter-layer organic ligands previously thought to be benign.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The princess and the pea: on the outsized role of inter-layer ligands in copper-pyrazine antiferromagnets

Kenny,

Jacko,

Powell

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…The exchange interactions in structurally homologous, chemically similar materials can often vary widely, , offering an opportunity to design and investigate materials by finely tuning their geometries. Although an abundance of experimental information is available for these materials, ,− the factors that control the magnetic interactions are still debated. To be able to design materials with specific sets of magnetic interactions, these factors need to be understood in great detail.…”

Section: Introductionmentioning

confidence: 99%

Tight-Binding Approach to Pyrazine-Mediated Superexchange in Copper–Pyrazine Antiferromagnets

2021

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We investigate the cause of spatial superexchange anisotropy in a family of copper-based, quasi-two-dimensional materials with very similar geometries. The compounds in this family differ mainly in their inter-layer separation but they have very different magnetic interactions, even within the basal plane. We use density functional theory and Wannier functions to parameterize two complimentary tight-binding models and show that the superexchange between the Cu2+ ions is dominated by a σ-mediated interaction between hybrid Cu–pyrazine orbitals centered on the copper atoms. We find no correlations between the strength of this exchange interaction and homologous geometric features across the compounds, such as Cu and pyrazine bond lengths and orientations of nearby counterions. We find that the pyrazine tilt angles do not affect the Cu–pyrazine–Cu exchange because the lowest unoccupied molecular orbital on pyrazine is at a very high energy (relative to the frontier orbitals, which are Cu-based). We conclude that careful control of the entire crystal structure, including non-homologous geometric features such as the inter-layer organic ligands, is vital for engineering magnetic properties.

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“….1).Of all the compounds, Compound 4 has received the most attention in the literature. It has been extensively studied experimentally[184][185][186][187]. BS-DFT calculations were performed on Compound 4 by Vela et al[29], showing that the two distinct Cu-pyz-Cu superexchange interactions within the planes differ by 25%.…”

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confidence: 99%

Derivation of effective low-energy Hamiltonians for chemically complex materials from first principles

Kenny¹

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List of Figures xiii List of Tables xviii2.1 Quasi-one-dimensional, temperature-dependent magnetic susceptibility of coupled spin-1/2 Heisenberg antiferromagnetic chains using the CRPA (Equation 2.14) and one-dimensional data from Eggert et al. [8,9] (in the place of χ chain ). The interchain coupling values are represented as a sum of all interchain couplings in the system, J ⊥i , divided by the intrachain coupling, J. In this case, the interchain couplings are all unfrustrated (c.f. Figure 2.2a). The dashed lines indicate that the CRPA is valid only above the temperature at which the system orders due to the interchain coupling (k B T i J ⊥i

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Room-temperature structural phase transition in the quasi-2D spin- 12 Heisenberg antiferromagnet Cu(pz)2(ClO4

Cited by 3 publications

References 26 publications

The princess and the pea: on the outsized role of inter-layer ligands in copper-pyrazine antiferromagnets

The princess and the pea: on the outsized role of inter-layer ligands in copper-pyrazine antiferromagnets

Tight-Binding Approach to Pyrazine-Mediated Superexchange in Copper–Pyrazine Antiferromagnets

Derivation of effective low-energy Hamiltonians for chemically complex materials from first principles

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