Magnetostructural Correlations in a Layered Perovskite: K₂CuF₄ at Large Compression

Abstract

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.