Neutron investigation of the magnetic scattering in an iron-based ferromagnetic superconductor

TL;DR

This study uses neutron scattering techniques to investigate the magnetic properties of an iron-based ferromagnetic superconductor, revealing inhomogeneous ferromagnetic order and vortex lattice behavior below specific temperatures.

Contribution

It provides detailed neutron scattering analysis of magnetic scattering and vortex behavior in an iron-based ferromagnetic superconductor, highlighting the coexistence of ferromagnetism and superconductivity.

Findings

Ferromagnetic order appears below 12.5 K.

Vortex lattice scattering observed at expected wave vectors.

Ferromagnetic moment is small and does not significantly affect vortex scattering.

Abstract

Neutron diffraction and small angle scattering experiments have been carried out on the double-isotopic polycrystalline sample (7Li0.82Fe0.18OD)FeSe. Profile refinements of the diffraction data establish the composition and reveal an essentially single phase material with lattice parameters of a= 3.7827 {\AA} and c= 9.1277 {\AA} at 4 K, in the ferromagnetic-superconductor regime, with a bulk superconducting transition of TC = 18 K. Small angle neutron scattering (SANS) measurements in zero applied field reveal the onset of ferromagnetic order below TF ~ 12.5 K, with a wave vector and temperature dependence consistent with an inhomogeneous ferromagnet of spontaneous vortices or domains in a mixed state. No oscillatory long range ordered magnetic state is observed. Field dependent measurements establish a separate component of magnetic scattering from the vortex lattice, which occurs at the expected wave vector. The temperature dependence of the vortex scattering does not indicate any contribution from the ferromagnetism, consistent with diffraction data that indicate that the ordered ferromagnetic moment is quite small.