Magnetostructural Correlations in a Layered Perovskite: K₂CuF₄ at Large Compression

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 K2CuF4, a prototypical 2D ferromagnetic system. Around 10 GPa sliding of [CuF4]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 K2CuF4 retains its layered and semiconducting character up to the boundary of its thermodynamic stability.