Coexistence of superconductivity and magnetism in FeSe1−x under pressure

Abstract

An extended investigation of the electronic phase diagram of FeSe1−x up to pressures of p≃2.4 GPa by means of ac and dc magnetization, zero-field muon spin rotation (ZF μSR), and neutron diffraction is presented. ZF μSR indicates that at pressures p≥0.8 GPa static magnetic order occurs in FeSe1−x and occupies the full sample volume for p≳1.2 GPa. ac magnetization measurements reveal that the superconducting volume fraction stays close to 100% up to the highest pressure investigated. In addition, above p≥1.2 GPa both the superconducting transition temperature Tc and the magnetic ordering temperature TN increase simultaneously, and both superconductivity and magnetism are stabilized with increasing pressure. Calculations indicate only one possible muon stopping site in FeSe1−x, located on the line connecting the Se atoms along the c direction. Different magnetic structures are proposed and checked by combining the muon stopping calculations with a symmetry analysis, leading to a similar structure as in the LaFeAsO family of Fe-based superconductors. Furthermore, it is shown that the magnetic moment is pressure dependent and with a rather small value of μ≈0.2μB at p≃2.4 GPa.

Source-reported materials — not catalogue approval

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