Commensurate antiferromagnetic ordering in $\text{Ba}{\left({\text{Fe}}_{1-x}{\text{Co}}_x\right)}_2{\text{As}}_2$ determined by x-ray resonant magnetic scattering at the $\text{Fe}K$ edge

We describe x-ray resonant magnetic diffraction measurements at the $\text{Fe}K$ edge of both the parent ${\text{BaFe}}_2{\text{As}}_2$ and superconducting $\text{Ba}{\left({\text{Fe}}_{0.953}{\text{Co}}_{0.047}\right)}_2{\text{As}}_2$ compounds. From these high-resolution measurements we conclude that the magnetic structure is commensurate for both compositions. The energy spectrum of the resonant scattering is in reasonable agreement with theoretical calculations using the full-potential linear augmented plane-wave method with a local density functional.

Figure 1

(Color online) (a) Diffraction data from the parent ${\text{BaFe}}_2{\text{As}}_2$ compound characteristic of the tetragonal structure above and the orthorhombic structure below $T_S=136\text{K}$. (b) Scattering measured in the $\sigma \text{−}\pi$ channel at the magnetic Bragg peak position of the “stripelike” AFM phase above and below $T_N=T_S$. (c) The temperature dependence of the integrated intensity of the magnetic peak in (b) normalized to the (1 1 8) charge reflection.

Figure 2

(Color online) (a) $\left[\zeta \zeta 0\right]$ scan through the magnetic Bragg peak position of the stripelike AFM phase at above (55 K) and below (20 K) $T_N$ for the $\text{Ba}{\left({\text{Fe}}_{0.953}{\text{Co}}_{0.047}\right)}_2{\text{As}}_2$ sample. The solid bar represents the experimental resolution for the x-ray measurements along this direction while the dashed bar denotes the resolution of our previous neutron measurements along this direction (Ref. 22). (b) $\left[\zeta -\zeta 0\right]$ scan through the magnetic Bragg peak position below $T_N$. The solid bar represents the experimental resolution along this direction for our x-ray measurements. The resolution width for neutron measurements (Ref. 22) along $\left[\zeta -\zeta 0\right]$ is a factor of ten larger. (c) and (d) correspond to (a) and (b), respectively, at the base temperature of 4.5 K. The difference in the vertical scale between panels (a), (b) and (c), (d) arises from small differences in the beam conditions for measurements performed several months apart.

Figure 3

(Color online) (a) Energy scans through the ${\left(\frac{1}{2}\frac{1}{2}7\right)}_T$ magnetic peak above (filled triangles) and below (filled circles) $T_N$, and at low temperature away from the magnetic Bragg peak (open squares) (b) The measured fluorescence (filled circles) and calculated absorption (line) as described in the text. (c) The background subtracted and absorption corrected XRMS signal (filled circles) along with the calculated XRMS spectrum (line).