Magnetic form factor of SrFe$_2$As$_2$

TL;DR

This study uses neutron diffraction to analyze the magnetic form factor of SrFe2As2, revealing isotropic behavior and slight elongation toward arsenic atoms, with no detectable lattice change at the phase transition.

Contribution

It provides detailed neutron diffraction data on the magnetic form factor of SrFe2As2, highlighting orbital occupation and spin density distribution in this parent compound.

Findings

Magnetic form factor is approximately isotropic.

Spin density shows elongation toward As atoms.

No detectable c-axis lattice change at phase transition.

Abstract

Neutron diffraction measurements have been carried out to investigate the magnetic form factor of the parent SrFe2As2 system of the iron-based superconductors. The general feature is that the form factor is approximately isotropic in wave vector, indicating that multiple d-orbitals of the iron atoms are occupied as expected based on band theory. Inversion of the diffraction data suggests that there is some elongation of the spin density toward the As atoms. We have also extended the diffraction measurements to investigate a possible jump in the c-axis lattice parameter at the structural phase transition, but find no detectable change within the experimental uncertainties.