Structural Changes and Jahn–Teller-Effect of K<sub>2</sub>CuF<sub>4</sub> under Pressure

Through a combination of Raman spectroscopy and synchrotron powder X-ray diffraction measurements supplemented with Density Functional Theory calculations, we unravel the pressure response of K 2 CuF 4 , a prototypical 2D ferromagnetic system. Around 10 GPa sliding of [CuF 4 ] 2− ∞ layers leads to a transition from the Ruddlesden− Popper phase into a Dion−Jacobson-like structure. This transition results in substantial structural and electronic rearrangement within the planes, resulting in a change from 2D ferromagnetism to 1D antiferromagnetism. Further compression induces tilting distortions that result in the transition into a novel P1̅ phase commencing at 15 GPa. The triclinic phase retains the 1D antiferromagnetic character, albeit with an alternating strength of the superexchange interactions. We show that K 2 CuF 4 retains its layered and semiconducting character up to the boundary of its thermodynamic stability.

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Compounds Containing Tetragonal Cu²⁺ Complexes: Is the d_x²–y²–d_3z²–r² Gap a Direct Reflection of the Distortion?

García‐Fernández

Barriuso

Garcı́a-Lastra

et al. 2013

J. Phys. Chem. Lett.

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It is widely assumed that the gap, Δ, between d x 2 −y 2 and d 3z 2 −r 2 orbitals in fluorides and oxides containing tetragonal Cu 2+ or Ag 2+ complexes directly reflects the tetragonal distortion in the MX 6 complex (M = d 9 ion; X = F − , O 2− ). This assumption on that relevant quantity is shown to be not correct through the study of pure K 2 CuF 4 -, KCuF 3 -, and Cu 2+ -doped KZnF 3 and K 2 ZnF 4 model compounds. Indeed, ab initio calculations prove that Δ in these insulating materials also depends on the internal electric field created by the rest of lattice ions on active electrons confined in a given CuF 6 4− complex. This internal field, especially important for layered compounds, is shown to explain all puzzling experimental facts on the d−d transitions of the studied systems and is of interest in the search of new Cu 2+ and Ag 2+ superconducting materials where a strong correlation between Δ and the transition temperature, T c , has been conjectured.

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Structural Changes and Jahn–Teller-Effect of K₂CuF₄ under Pressure

Cited by 5 publications

References 12 publications

K2CuF4

K2CuF4

Magnetostructural Correlations in a Layered Perovskite: K₂CuF₄ at Large Compression

Compounds Containing Tetragonal Cu²⁺ Complexes: Is the d_x²–y²–d_3z²–r² Gap a Direct Reflection of the Distortion?

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Structural Changes and Jahn–Teller-Effect of K2CuF4 under Pressure

Cited by 5 publications

References 12 publications

K2CuF4

K2CuF4

Magnetostructural Correlations in a Layered Perovskite: K2CuF4 at Large Compression

Compounds Containing Tetragonal Cu2+ Complexes: Is the dx2–y2–d3z2–r2 Gap a Direct Reflection of the Distortion?

Contact Info

Product

Resources

About

Structural Changes and Jahn–Teller-Effect of K₂CuF₄ under Pressure

Magnetostructural Correlations in a Layered Perovskite: K₂CuF₄ at Large Compression

Compounds Containing Tetragonal Cu²⁺ Complexes: Is the d_x²–y²–d_3z²–r² Gap a Direct Reflection of the Distortion?