Spiral magnetism, spin flop, and pressure-induced ferromagnetism in the negative charge-transfer-gap insulator Sr2FeO4

Peter Adle, Manfred Reehuis, Norbert Stüßer, Sergey A. Medvedev, Michael Nicklas, Darren C. Peets, Joel Bertinshaw, Christian Kolle Christensen, Martin Etter, Andreas Hoser, Liane Schröder,, Patrick Merz, Walter Schnelle, Armin Schulz, Qingge Mu, Dimitrios Bessas, Aleksandr Chumakov, Martin Jansen, Claudia Felser

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Iron(IV) oxides are strongly correlated materials with negative charge-transfer energy (negative Δ), and exhibit peculiar electronic and magnetic properties such as topological helical spin structures in the metallic cubic perovskite SrFeO3. Here, the spin structure of the layered negative-Δ insulator Sr2FeO4 was studied by powder neutron diffraction in zero field and magnetic fields up to 6.5 T. Below TN=56K, Sr2FeO4 adopts an elliptical cycloidal spin structure with modulated magnetic moments between 1.9 and 3.5 μB and a propagation vector k=(τ,τ,0) with τ=0.137. With increasing magnetic field the spin structure undergoes a spin-flop transition near 5 T. Synchrotron 57Fe-Mössbauer spectroscopy reveals that the spin spiral transforms to a ferromagnetic structure at pressures between 5 and 8 GPa, just in the pressure range where a Raman-active phonon nonintrinsic to the K2NiF4-type crystal structure vanishes. These results indicate an insulating ground state which is stabilized by a hidden structural distortion and differs from the charge disproportionation in other Fe(IV) oxides.
Original languageEnglish
Article number054417
JournalPhysical Review B
Volume105
Number of pages10
ISSN2469-9950
DOIs
Publication statusPublished - 17. Feb 2022
Externally publishedYes

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